Comcast Blocking Port 25 Without Notice (Updated)

Comcast this weekend did something nice to me (not). They blocked my Port 25, without any notice at all.

Now, I don’t use port 25 on most email accounts, I use SSL email over port 587. But, plenty of people do use it.

Worse, Comcast Tier 2 support hasn’t been informed that they are blocking port 25, nor do they have any idea of what to do if your email provider relies on Port 25 (as in, you can’t use another port).

Port 25 blocking has become a popular way to reduce the tide of spam and viruses, which commonly use Port 25. The majority of major ISP customers use web mail, and as such aren’t impacted by these blockings.

Now, I don’t know if I’m simply unlucky, and this is a glitch on my account… or if this is the start of a company-wide move. So, let me know if Comcast is blocking Port 25 on you in the comments.

Update: Looks like I’m definetely not alone. If you see this posting [note: profane language], the comments start around early April, and new Port 25 blocks run through this week. Clearly, Comcast is deploying new Port 25 blocks, and clearly they have no protocol for unblocking.

That’s not good Comcast, I’ll give it (my trouble tickets) a week, then it’s FCC Complaint time.

51 Responses

  1. Daniel H.
    Daniel H. May 12, 2008 at 12:22 pm |

    sorry man, i’ll pretty much always use webmail for this sort of reason. what if i move and change providers? that sort of thing never quite sat well with me.

  2. Christopher Price
    Christopher Price May 12, 2008 at 12:49 pm |

    I for one never use webmail systems… they’re unreliable and less secure. Someone shouldn’t make email choices based on an internet provider’s faulty implementations… instead, we need to pressure Comcast to fix this.

    The line of thought is dangerous, since one could say that you shouldn’t innovate new technologies (BitTorrent) since Comcast “might” block it.

    Thanks to IMAP, I can take advantage of the benefits of webmail (having all your email on every device) combined with the benefits of a desktop client (address book integration, spelling and grammar check, and searching inside of every email via file search… Spotlight on Mac, and Windows Desktop Search on PC).

    AT&T had similar issues when they blocked Port 25. Now all it takes is filling out a form to unblock via request on AT&T.

  3. Ken Anders
    Ken Anders May 16, 2008 at 11:09 am |

    Comcast just blocked me as well. I cannot stand that they do this without notice. Someone spoofed my email but there are not background email transfers running from my systems and I am not a spammer. If you have any suggestions on using Outlook to a safe SMTP mail server, that would be great.

  4. Christopher Price
    Christopher Price May 16, 2008 at 4:50 pm |

    If your email provider supports SMTP with SSL, you can try turning that on and using port 587. Comcast certainly isn’t blocking that port…

    However, if your email provider doesn’t support that, your only option is to call your email provider and hope that they have opened a secondary port.

  5. Ian Argent
    Ian Argent May 19, 2008 at 9:12 am |

    I’ve been port-25-blocked for quite some time now. My provider supports a couple of alternate ports, so I just chalked it up to security and wen ton. It’s not like Comcast is any kind of innovating here – Cox has been blocking port 25 for quite some time.

  6. Dan
    Dan June 4, 2008 at 8:35 am |

    Comcast started blocking port 25 for us (Savannah, GA) last night–6/3/2008.
    Their tech support was very unhelpful as usual, but I did wast about 2 hours with them.
    I finally got around it for now by switching to port 587, but I think it’s more than time to check into alternative Internet suppliers.
    I don’t like companies that arbitrarily restrict my usage like that.

  7. Teri
    Teri June 7, 2008 at 4:01 am |

    I had the surreal experience this past week of suddenly being unable to send mail from either of two “” accounts I have–both of which are set up for pop3 access through my Outlook2007. Comcast is my ISP.

    After scrutinizing my Outlook settings, I noticed my Comcast email account had a port setting for 587 (SMTP) and my other accounts were on 25. Since I couldn’t get a live person for my other email accounts (and I HATE dealing with Comcast), as a lark I tried changing the SMTP ports for the “problem” accounts to 587.

    Voila, and “hmmmm”. I called Comcast, who claimed they had switched ports months ago and couldn’t imagine why I was having trouble all of a sudden. I suspect they switched mine at the exact time I started having problems and didn’t tell me. Worse, it looks like they are now lying about it.

    I freakin’ HATE dealing with Comcast. If you get a friendly AND knowledgable person, you are lucky.


  8. Teri
    Teri June 7, 2008 at 4:06 am |

    One more thing…

    I don’t have a problem with their blocking the port, but I DO have a problem with their not notifying customers so they can prepare. That’s just plain rude.

    It’s like cutting off any utility with no notice as to what the problem is.


  9. ZOOM
    ZOOM June 12, 2008 at 2:58 pm |


    Some ISP’s such as comcast are starting to block the default SMTP port 25. As an alternative you can try port port 587 … to do this try or

    Another option is to configure your server to use a free SMTP outgoing service like gmail make sure to use SSL for port 587

    Incoming Mail (POP3) Server – requires SSL:
    Use SSL: Yes
    Port: 995
    Outgoing Mail (SMTP) Server – requires TLS: (use authentication)
    Use Authentication: Yes
    Use STARTTLS: Yes (some clients call this SSL)
    Port: 465 or 587
    Account Name: your Gmail username (including
    Email Address: your full Gmail email address (
    Password: your Gmail password

  10. michel
    michel June 18, 2008 at 6:02 pm |

    Well I have been block on inbound 25 yesterday
    Calling Comcast they says this is a VIOLATION of the policy to have an email server on a residential plan

    Grrrrr… there is no way around !

  11. Ben
    Ben June 21, 2008 at 2:15 pm |

    Blocking 25 in Northwest

  12. mb
    mb June 23, 2008 at 11:09 pm |

    25 blocked here in the East Bay area of San Francisco Bay

  13. mb
    mb June 24, 2008 at 12:04 am |

    it’s about midnight, and suddenly 25 is unblocked…..go figure….I’m it sure it isn’t a case of Comcast’s decency to its customers or bowing to public outcry. Am sure it’s caprice…….again.

    Is anyone else “cured”?

  14. Ray
    Ray June 24, 2008 at 10:15 am |

    My comcast account became blocked and I switched to port 587 after surfing various forums like this one. Although some say port 465 works for outgoing (along with ‘my server requires authentication’ which I’ve never needed in the past).

    I fear that many of my web design customers will have same problem. Just got call from one with same problem, but he uses Verizon, so it only gets worse. My Host can’t give me good suggestion.

  15. Bonnie
    Bonnie June 25, 2008 at 8:23 am |

    My comcast account is blocked (chicago) for outgoing email- and I am just now educating myself on this whole issue- kind of a newbie. Is there anyone out there who can fill me in on the issue of ‘open relay’? I would like to be able to find out if my account is being used so I can fix that. I am a Mac user- any help would be greatly appreciated. Seems to me, a better solution to the whole spam issue would be to help consumers safeguard their accounts to keep the spammers out- rather than just blocking everyone. I am not an expert by any stretch of the imagination, but it just seems like laziness on the part of the ISPs…


  16. Mike
    Mike June 30, 2008 at 5:11 am |

    Comcast in the Boston area starting blocking ports this weekend, yesterday I think (6/29)!

    They are blocking BOTH inbound AND outbound SMTP AND they are blocking relays through their SMTP servers. Ugh, I’m about to get on the phone with them and NOT looking forward to it.

    The thing that really ticks me off is I have both residential and commercial accounts with them. The commercial account has static IPs. I wanted to get COMMERCIAL internet with RESIDENTIAL phone and TV (because you can’t get premium TV channels on a COMMERCIAL account) and they couldn’t configure my account that way! In their pea-brain world you have to be EITHER a Reisdential OR Commercial customer (I guess they haven’t quited grasped this whole “running a business at home” thing just yet…..!!!).


  17. Dan
    Dan June 30, 2008 at 8:54 am |

    Comcast started blocking me in Boston between 1:00AM-6:30AM on 06/28/08, inbound and outbound on port 25. I’ve run my mail server for my business at home for years. The dynamic ip only changed once maybe twice a year.

    I just called Comcast and ordered a static ip commercial service. They didn’t seem to have any problems with two bills going to the same address. (residential tv and commercial internet)

  18. Ray
    Ray July 17, 2008 at 10:49 am |

    Here’s a possible fix. It worked for me (at least for now) for one of my webmail “added” accounts. I got this from a comment at

    In Outlook, go to: Tools..Email Accounts..(select one)
    Double click the email acct you want to alter
    All email accounts must have as the outgoing mail server.
    Click More Settings..Outgoing Server tab
    Check My Outgoing Server requires authentication
    Check Log On Using and type in your Comcast username and password.
    Click Advanced tab and change your Outgoing Server to 587
    Click OK and then click Test Account Settings and you’ll be fine.

  19. Chuck
    Chuck July 18, 2008 at 8:52 am |

    After reading these forums concerning Comcast’s port 25 issue, it seems that we may need to be more specific on the “mail server” location and access point.

    What I mean is, some people say that Comcast is blocking their server from sending mail, where is the server? Is the server actually in your home or are you using a server at a remote location/company like ipower or godaddy?

    Comcast can not block the remote server. They can only block your computer at your home (IP) when using a third party mail program such as outlook. What I am saying is that they are interrupting your communication with your server when you are trying to send mail. Your web mail works because you are sending from the server which is not using comcast and not from your computer which is.

    Today I filed complaints with the FCC and the New Jersey Board of Public Utilities. I hope everyone here will take the time to do the same.

    Comcast is using their monopoly power for social engineering. Comcast decides what we can and can not use the internet for. The FCC has just fined or is about to fine comcast for its practice of blocking file transfers they didn’t like.

    I am not a lawyer but maybe comcast’s interference with us doing business with our server providers is an abuse of their monopoly power and a violation of the anti-trust laws.

    Obviously, I would like to hear everyone’s thoughts on what I have written even if you disagree.

    I think that I will pursue the legal concept of comcast’s violation of the anti-trust laws.

  20. B.M.
    B.M. July 24, 2008 at 7:17 pm |

    Grrrr . . . I just uncovered this issue. I’m totally annoyed and clueless. So if my e-mail is how am I supposed to send if I can’t use the outgoing comcast server anymore and I’m using something like gmail? Any suggestions in non techie speak?

  21. Stan
    Stan August 1, 2008 at 7:51 am |

    Just started getting outbound email blocked (worked fine until now). I have mail using GoDaddy domain, now can’t logon to port 587 Comcast helpdesk says that I have to use as my POP3. tried to get a supervisor, but was told they were busy. anyone find a solution to this?

  22. Michael
    Michael August 2, 2008 at 5:47 am |

    Stan, try using port 80 for your Godaddy email account. I found that suggestion of the GoDaddy website and it fixed my problem.

  23. bruce
    bruce August 17, 2008 at 2:17 pm |

    Comcast started blocking port 25 in Alpharetta, GA on 8/13/2008.

  24. Michael
    Michael August 17, 2008 at 4:48 pm |

    I fully agree with Chuck and also filed a complaint with the FCC alleging anti-competitive behavior on
    the part of Comcast.

    By requiring non-Comcast companies to use something other than port 25, Comcast is engaging in social engineering and anti-competitive behavior. While they allow a user to “relay” a message through their mailservers, many email providers check the SPF records ( and/or SenderID records ( to determine if Comcast is an authorized sender for the sender’s email domain. Comcast is not an authorized sender for non-Comcast mailservers that I use which means that outbound messages would be blocked by the recipient’s mailserver if they check SPF or SenderID records.

    I also sent an email to Brian Roberts ( who is the CEO of Comcast. I included the FCC complaint number, a copy of the complaint, and a copy of the chat that I had with one of their employees. By 10:00 AM the next morning, I received a voicemail message from “Comcast Internet Security” (888-565-4329) who left me a ticket number. When I called them back, they asked me a few questions and then agreed to remove the Port 25 block. They explained that a block can occur if they see spam coming from my IP address, OR if any comcast email user marks an email from you (whether faked or not) as Spam. One time, thats all it takes.

    Within an hour or so, my port 25 access was restored. Two days later, however, port 25 was blocked again. I’ve already confirmed that spam is not originating from my IP, so someone must be using my email address to send out spam. It appears that Comcast is either allowing someone to send email through their mailservers using my email address, OR Comcast is accepting email messages (allegedly from me) from non-Comcast mailservers. In either case, it is a Comcast problem but I’m the one who is being punished.

    Having said all that, I did learn that many ISP’s are now blocking Port 25 (see Any mailservers that are not providing alternate SMTP ports are very outdated. I’ve already gotten one of my non-Comcast email providers to create a new SMTP port, and I’m working on the other. I think I’ll have better luck there than dealing with Comcast.

  25. John Kelly
    John Kelly October 3, 2008 at 12:44 pm |

    Chalk up another one — Comcast did the same thing to my employer. No notice, no nothing, and when we called to say “stop blocking port 25” their support person assured me they weren’t blocking it. I had to set up a couple of remote telnet sessions from external hosts (thank God for ssh) and call them back and prove it to them.

    Morons! I can understand why they’d block port 25, but they ought to tell their customers when they do it. Fortunately we won’t be their customer much longer.

  26. Tim
    Tim October 5, 2008 at 5:00 pm |

    Same here, in Richmond, VA as of 10/5.

    I called Comcast customer service and they had me change to port 587. That did the trick.

    I then logged into my Comcast email account and found the same “Customer Security Assurance Notice” that others have received, claiming that “Comcast has determined that your computer(s) have been used to send unsolicited email (“spam”), which is generally an indicator of a virus. For your own protection and that of other Comcast customers, we have taken steps to prevent further transmission of spam from your computer(s).”

    The customer service rep also indicated that this often happens to customers who send “a lot mail” (his words).

  27. jones
    jones October 9, 2008 at 7:56 am |

    Comcast has lost almost all neighborhood business to Verizon FIOS.
    2-year contract prevents me fro dealing with Verizon.
    I am the last Comcast hold out on my block I guess.
    Oct 6. port 25 dead.
    465/SSL seem to work
    then they ghost everthing to the NSA

    Going to have to tunnel everything from now on to my offshore shell account

  28. Christopher Price
    Christopher Price October 9, 2008 at 2:28 pm |

    Jones, you can use these blocks as a contract violation… thus freeing you from your contract sans any early termination fees.

    A couple of firm-but-polite calls to customer service should take care of that. If not, it’s BBB and FCC complaint time.

  29. Richard
    Richard October 17, 2008 at 1:30 pm |

    Just happened to us last night. I called and threatened to cancel the service and they said. “Ok, sorry to see you go.”

    Looking for another ISP right now.

  30. Robert
    Robert November 13, 2008 at 10:46 am |

    Comcast wants everyone to leave them…… so they can apply for the same help all the finance companys and home loan companys are getting to bail them out…. FREE MONEY!!!!

    All kidding aside, same problem here, two times since Friday.

    When the problem first occurred (Friday morn) we were having problems uploading a website to two known working ~comcastsites…. we figured they were doing maintenance, till it still didn’t work on Sunday. Phone call, while on hold I found the port 25 problem, two hours later here is what I was told, you can send 1000 emails a day before you get blocked. The tech could not help me and said the block should only last 48 hours, which it did fix itself about that time. She did put in a ticket about the website problem and that was resolved by Wednesday night. No contact at all saying the problems were fixed, per say.

    Port 25 block occurred again and was noticed Thursday morning. Another call and the tech removed the block immediately. He said the daily limit was 100 emails. He’s probably correct, as he seemed to know what was going on and answered questions immediately.

    Almost $180 a month in TV, phone and Internet charges and this is what I get…. Fios is not available in my area yet. Just the standard 1.5Mbps DSL option, unless I want a business line, $$$$$.

  31. Scott
    Scott November 14, 2008 at 12:37 am |

    Just noticed my PORT 25 blocked on 11.13.2008 in N.W. Alabama. Got the same crap as everyone else

    “Customer Security Assurance Notice” that others have received, claiming that “Comcast has determined that your computer(s) have been used to send unsolicited email (”spam”), which is generally an indicator of a virus. For your own protection and that of other Comcast customers, we have taken steps to prevent further transmission of spam from your computer(s).”

    What gets me why do they send these bogus emails to me about my computer sending mail. No program is allowed access to the net through the firewall unless I know its connecting. Why don’t they just say…we are blocking port 25 and be through with it. Lies, Lies and more Lies! Before I knew what was going on I called Comcast and the girl I spoke with had no idea they were doing it! She was very nice though…guess I was one of the lucky ones! 🙂

    Looks as though Comcrap is going to keep pushing the envelope to see how far they can go, not to mention what they can get away with! Makes me sick! AT&T DSL is just up the road and coming this way, but from what I hear not sure they are any better!!

    I hope the FCC gives them more than a slap, I am also tired of my Bit Torrent traffic being shut down. They say they only shape during peak hours, well in my neighborhood of 15 homes 10 have Comcast. I never use BT during the day, but after 11:00 I know most people are through for the day I get on BT and they still throttle!


    Anyone ready to start a new ISP with me!??

  32. Anon
    Anon November 16, 2008 at 11:15 pm |

    I think in regards to the poster whom stated he had his port 25 re-opened, just to have it closed two day later….would show we are forgetting how computers work.
    If a comcast subscriber marking an email as “spam” puts the senders account into port 25 blocked status, I think there’s something forgotten:

    Alot of “novice” computer users which are the majority dare I say, quite regularly “mark as spam” emails they wish to delete from friends and family…etc.
    Which would kick alot of people into being blocked especially if the system reads the attached addresses in forwards (jokes, cute emails etc)

    Even if blocked, and if being auto sent into the spam of someone’s email, (maybe they didn’t like the joke fowards) …. upon sending the next “regular” email again, it would auto detect the spam filter usage each time and perhaps with the attached associated email.

    Guess spam means no more forwarded jokes etc? (That’ll make alot of grandparents sad ^^).

  33. Patrick
    Patrick November 22, 2008 at 10:46 am |

    This morning I received an “ACTION REQUIRED: Comcast has determined that your computer(s) have been used to send unsolicited email (“spam”), which is generally an indicator of a virus” message from Comcast Customer Security Assurance (CCSA).

    The message tripped my spam filter and was routed to my junk email box. For some reason, I was curious enough to see what spam had been delivered – I usually don’t look. The message was not personally directed and the content was generic enough that I thought it was really spam or a hoax (good job Comcast). As a test, I sent an email to myself, no errors, but 5 minutes later, still no echo. Hmmm.

    So, I called Comcast Tech Support…

    I should have received 4 emails warning of a pending change – those were likely also routed to my spam box (if they were sent at all). The support agent told me that after Comcast made the change (which occurred over a week ago), I was allowed 25 emails (not 25 per hour, or 25 per day, but 25 total since the switch) on the old port. The 26th would block my ability to send email on port 25 and trigger the “you probably have a virus” email from CCSA.

    I applaud the effort to block spammers, but, this could have been handled much better. The warning and final emails from CCSA could have been written to not trip ‘normal’ spam filter settings. The “you probably have a virus” email caused me to do multiple scans on 3 different computers looking for a spamming agent that was not there (Thanks CCSA!!).

    Who knows if the Comcast support agent gave good info – it seems like I get a different story every time I call.

  34. Deborah
    Deborah November 28, 2008 at 6:52 am |

    I just experienced this problem on all days, Thanksgiving.
    We couldn’t send any mail but could receive mail. Comcast is my internet provider but they are not who we go through for our e-mail. We have 2 domains through IX Webhosting and it’s their servers that our e-mails go through. I first contacted them and found out that they don’t block Port 25 but that they have this problem coming past there help desk everyday due to Comcast blocking this port. I then contacted Comcast and simply explained that 1) I wasn’t about to change anything on my end since it has been working perfectly fine for well over 10+ years and 2) I wanted to know why my modem (which belongs to Comcast due to us upgrading a year ago to the digital voice) was selected and Port 25 was all of a sudden blocked. They couldn’t of course tell me why they did this but they did unblock it.

    So, if you go through Comcast’s servers to get your e-mail then yes, Port 25 is blocked and you’ll have to set your out going to 587 but if you don’t go through Comcast’s servers for your e-mail and you use their modem, then this is were the block on Port 25 occurs. Call them and ask that the block on your modem be removed and more than likely it will be done in seconds. Problem with them doing all of this is that some of us (including myself) have no clue to what to say to get this problem rectified. The only why I found out was due to the help desk at our hosting company about the block but it was search on Google that I that talked about Comcast selecting certain modems and blocking Port 25 that way.

  35. Sy
    Sy November 29, 2008 at 3:09 pm |

    when they give you another port to go to for out going, its a port that they have access to (as far as their software) , to snoop out various information that is part of the domestic wiretapping policy-
    I work in the IT industry, and this is what we do if we want to watch someone’s email or ‘port’ activity with a close eye on various key indicator such as bandwidth, email content, spam origin and destination.
    Frustrating as it seems, but just know that when you rent their equipment, they can do as they want, but if you own it and they make the change without your authorization, then you have a legitimate claim of tort against them for tampering with YOUR equipment, they are obligated to notify you of what, when, and why they need to make a firmware update on your modem.
    suggestion: buy your own, and notify them that you own this modem, and do NOT wish for them to upgrade it at all, but to enable it access to their domain.
    if they refuse, then you can refuse payment of service that does not satisfy their own ToS.

  36. Christopher Price
    Christopher Price November 30, 2008 at 2:01 am |

    Sy, they do not need to update your cable modem to filter a port. And, if you refuse to pay… it’s just going to open a mess. First, Comcast will cut off your service (including TV and Phone if you use Comcast for those).

    I do not suggest withholding payment in this case. Instead, I suggest submitting an FCC complaint, and a complaint to your state’s Public Utilities Commission. Finally, I would change providers and move on. If you withhold payment, all you’ll wind up doing is fighting to keep the charge off of your credit record.

    And, since Comcast is already imposing a bandwidth cap… I’m already suggesting everyone leave Comcast in protest. Even AT&T is only testing the idea right now, and I would rather go with AT&T that is toying around with the idea… than Comcast that is imposing it.

  37. Sly
    Sly February 3, 2009 at 11:35 pm |

    Seattle area – January 3,2009, just got the port 25 email from Comcast this a.m. (in my junk email folder). Service cut today – what a hokey deal!!. This is the first I’ve heard of this, discovered this site after looking around to see if the email was a hoax etc or something. What a pain. Finally figured out how to change to port 587 – look on the comcast email, click on the blue “our client page” – there are several options for changing email settings. If you are not computer savvy check your pics are the same as theirs!! Sly

  38. malcom clapton
    malcom clapton February 16, 2009 at 7:26 pm |

    Comcast is a ******* nightmare. They make you spend five minutes to get “tech” help that tells you to switch to port 587. They say that will work, and it does not allow you send a busienss email from home using your .com accounts. Then by the fourth call I demanded a supervisor which took 36 minutes to get, and he said I need to call the fraud department. HELL, why tell me for 24 hours straight that you have ticket in and will call me with a fix if it was a fraud issue.

    Worse yet, my 2 year old equipment scan/fax machine from Kyocera that cost over $2,000 does not work on port 587. So I’ve got a ******* machine that won’t work anymore. What a bunch of ********. How can anyone work from home with this ********.

  39. Paula
    Paula February 24, 2009 at 10:23 am |

    I have been blocked on port 25 inbound. I am a geek and I have my own ‘home’ email server which I use to send myself photos I click on my telephone and sort on my ‘home’ gallery using the content in the email with the attached picture. I don’t see this as commercial, I don’t sell anyting, I’ m must using the Internet and I don’t think my incomming port 25 should be blocked. I’ve contacted comcast customer service and they said that the port is blocked because of spam. Spam? I don’t send anything out of this mail server! I specifically dissabled outgoing traffic. There is no way in hell that this server can relay mail or become a spam zombi. hello, comcast, what kind of service is this?

    Now it seems I have to pay some other service, like dyndns, to mail relay hop to another port address that is not blocked. WTF am I paying comcast for anyway?

  40. Jon
    Jon March 8, 2009 at 9:00 am |

    I just got blocked too — turns out I had a dang keylogger on my system! In a way, I have to say “thank god” that they DID block it, but once again, there was no notification, leaving me to figure out what was going on. Luckily I’ve dealt with this before, so I did figure it out pretty quickly.

    Just as an aside for “malcom” and others, above, you might consider a different router/gateway, like my Netgear, which can do “port translation”, which will allow traffic to come in on any port, and then translate that to a different port, internally. In laymans terms, this means that traffic would come into the gateway on 587, but the router would deliver that traffic to the specified device on port 25.

    Hope this helps!

  41. Frank
    Frank July 11, 2009 at 2:19 am |

    I got hit with this today.

    Their email displayed a link to a one-click fix for Outlook Express.

    I clicked on the link. The software ran. The fix failed to fix anything.

    Thanks a lot Comcast.

  42. Frank
    Frank July 11, 2009 at 7:14 am |

    A follow-up…..

    I spoke with Maurice in Tech Support. He knew how to resolve the problem and did so in two minutes. Excellent support!

    Basically the procedure was to go to Tools > Accounts >Properties > Advanced

    then change the Outgoing Mail (SMTP): to 587

    and also

    UNcheck the box for “This server requires a secure connection.”

    If that does NOT resolve the issue, go to the Tools >Accounts > Properties and click on other tabs up top to find a checkmark for a “server requires a secure connection or authentication” message and UNcheck it.

    That should do it.

    Thank you, Maurice.

  43. Christopher Price
    Christopher Price July 13, 2009 at 4:04 am |

    Frank, that only works with a few ISPs that allow unencrypted traffic over port 587.

    Good ISPs block unencrypted traffic over port 587, and require SSL. But, many don’t allow any SMTP traffic over port 587.

    Comcast has many workarounds, and they do work a lot of the time, or they wouldn’t be doing it. But, at the same time, they’re telling a lot of customers that they’re SOL. They need to offer a workaround (like AT&T does) for those customers.

  44. Frank
    Frank July 13, 2009 at 6:48 am |

    I posted, or at least thought I had posted, my comment on the Comcast website for Comcast customers to see.

    However, subsequent to that I found that the email on our laptop has the same type problem with Outlook Express, but the fix I posted doesn’t work on the laptop (XP with two Users). The Comcast tech support lady (Maurice wasn’t there) did not know how to fix the problem. She opened a Ticket with the issue.

    I’m not expecting anything good to come from the Ticket, but maybe I’ll be lucky.

    My workaround for the laptop is to go to the Comcast website and do email from there, not Outlook Express.

  45. Jon
    Jon July 13, 2009 at 9:25 am |

    Yeah, the issue with Comcast is not that there is not a work-around, the issue is that they make a work around necessary with no warnings or notifications. And, as you have found, once they do this, you must manually modify each and every one of your computers and/or applications which send email, because if you miss one, it will not work anymore.

  46. SMTP2525
    SMTP2525 September 7, 2009 at 5:55 pm |

    If you’re interested, check out Unified eMail. They provide secure SMTP Relay service over alternate port 2525.

  47. hathcock
    hathcock November 21, 2009 at 1:36 pm |

    I live in Hillsboro,NH and was just notified this morning:
    I have 3 computers, 2 which use Outlook on windows XP and a Vista using windows mail.
    The Vista computer is not acknowledged by their Comcast site for a fix to the email program.

    What Can I do???

    November 21,2009
    Customer Security Assurance Notice

    Dear Comcast High-Speed Internet Subscriber:

    Action Taken: In an effort to help prevent spam and ensure the security of our network and customers, Comcast has modified your modem’s settings to prevent the sending of email on port 25. That is the default port email programs such as Outlook Express use to send email. We’ve taken this action because we may have detected virus-like activity from your modem or received reports from other email providers that mail from your modem generated complaints from their users. Please read this message to understand how this action may impact your ability to send email and what you should do next.

    Comcast Webmail Users
    If you use a web browser to access your email, this action will not affect your ability to send or receive e-mail. This action also does not affect any non-Comcast webmail services.

    Email Program Users (Outlook Express, Outlook, MacMail, etc.)
    If you use an email program, this action will disable your program’s ability to send email until you change your email program settings to send email on port 587. Port 587 uses authentication and is an industry-recommended alternative to port 25. If you use Outlook Express and email, Comcast has provided a simple one click fix for you to use with Internet Explorer. If you use another email program such as MacMail, Eudora, or Thunderbird, please visit our client page for information on how to change the settings for sending email in your email program.

    If you are not using email and use another email provider, please contact your provider for its recommended port settings. Most email providers offer an alternative to port 25 for sending email.

    All Users

    To help protect your security and privacy, it is important to regularly check for and remove any possible viruses from your computer. You can do this using the McAfee Antivirus and Firewall software available from Comcast to subscribers at no additional charge or by using other popular antivirus solutions that are widely available. In addition, Comcast recommends that you secure any wireless network in the home and that the operating systems on your computers be updated regularly with the latest security enhancements. Please visit the security channel for more information and tips on how to enjoy a safe and secure online experience.

    If you have additional questions please visit (

    Thank you for choosing Comcast!

    Comcast Customer Security Assurance

  48. Jon
    Jon November 21, 2009 at 1:45 pm |

    Hey Hathcock,

    The fix still applies to Vista, just go to Tools/Accounts, select the account, and then Properties, then Advanced, and then you can change the port as required.

    Of course, do be sure to scan all of your computers for virii first, as you might actually have a spam bot installed!


  49. Asher Martin
    Asher Martin November 21, 2009 at 4:28 pm |

    google offers free SMTP and POP account setup… you can use that to bypass since they use different port numbers then the defaults used by SMTP or POP. I think this is because they have some STL or SSL login.

  50. Jenina
    Jenina May 20, 2010 at 3:36 pm |

    I have tried 25, 995, 80, 465, and 587. None of them are working. This is probably the 5th time I have dealt with this since I became a Comcast client.

  51. Joel
    Joel March 28, 2013 at 2:55 pm |

    Years later Comcast is still blocking 25 for no reason. I have been able to use port 25 outbound for a long time, but within the last month they have blocked it without warning. Apparently the FTC has done nothing about this problem.

    It isn’t Comcast’s job to prevent the use of unsecured SMTP servers. It is the owner of those servers’ problem. And if the server administrators can’t fix the problem then those servers get put on a blacklist.


Leave a Reply