Starting early this morning I was unable to send any email from my Mac. Late this afternoon, my wife said she had the same problem. I did some testing and determined that I couldn’t send to any SMTP host (not just Comcast’s host) on port 25. I could send email from my Gmail account, but that’s browser based. I did a little surfing and found a thread on Chris Pirillo’s site in which others have had the same problem.
It turns out that Comcast has blocked my outbound traffic to port 25 on any server. Did they inform me? No. Was there a reason for doing so? No. I use the smtp.comcast.net server for outbound mail, as they told me to when I signed up for their service years ago.
I called Comcast support and spoke to a useless tech. He said I should call Apple because there must be a problem with my Mail program. Oh, and my wife’s, too, of course. But the Lockergnome thread suggested I call Comcast’s security department at 856-317-7272, which turned out to be a good idea. The first thing the automated system tells you to do is go to www.comcastsupport.com/alternateport and download the OneClick fix. Okay, except it’s specific to Outlook Express. Doh! Another call to the security guys to talk to real people. These folks at least know what they’re talking about, and I was able to get back up and running.
Apparently, this is part of some ongoing program. Comcast disables outbound traffic to port 25 at the drop of a hat. Other ISPs do this, too, although I would hope they’d communicate first with their customers. The fix?
- Configure outbound email to smtp.comcast.net, but on port 587, not the default port 25.
- You must use password authentication for outbound/SMTP. Unless you’re using your ISP’s web mail, you probably forgot your username and password, so you’ll have to call the ISP to get them.
- Do not use SSL.
Alternatively, just do what so many people are doing and use Gmail.
Blogarithms 
I first wrote about this as well back in September of 2006 twhere I also included a list of known providers who where doing this
http://www.winextra.com/2006/09/18/gotta-love-bellnet-not/
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Is it supposed to be an anti-spam/anti-bot measure? If so, why not just demand authentication for outgoing mail? It’s a shame when Internet Service Providers stop providing certain Internet Services.
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Blocked by the web…..get used to it..work on bandwidth penetration..for the good of all who have something to say.
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First…let me fix my spelling sorry. My ISP (hughes.net a satellite ISP) cuts us down all the time. Even though there is lighted fiber .25 miles away I can’t tap in! Go figure.
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I am extremely steamed at Comcast. Sure, the port 587 is ok if you just use an email client…but my old Ricoh 4410NF fax won’t use any other port for scan to email…so Comcast has left me with an $1800 boat anchor. They first lie to me, tell me they don’t block the port, then they admit and say sorry…we will fix it…then they don’t! I am totally sympathetic to blocking spam, but my machines are no bots. I scan ’em and clean ’em often. Looks like I need a new ISP… Any suggestions out there?
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a way round this is to use your own internal company gateway to send email through your gateway to your remote mail service through a hosted website. ie my company host corporate sites and we do this for our customers. 404 474 3023
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Kevin – Comcast is blocking all traffic outbound on port 25 (and maybe inbound?) on every residential account I’ve come across in the past several months. While this may not matter to most people, it causes huge problems for others. 😦
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They hit me with this just recently. Claimed I sent out spam mail, but I’m guessing it was someone else at the same floating IP. ‘Their’ notification mail had misdirected links in it, and while trying to find out if it was a phishing attack or not, I got nothing but a runaround from their ‘security’ section via email. Thanks for summarizing the problem; changed the port in Thunderbird, and things work fine (I’ve always used auth).
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Thank you guys! I swear I thought I was loosing my mind. I had just added my second Slingbox to my router and recently downloaded BitTorrent…I was lost as to why suddenly I couldn’t send e-mails after it worked so perfectly for 2 years. Thanks for the info, e-mails are now sending perfectly.
So if I’m reading everyone correctly, Comcast is doing this because we are “sending spam”??? Not one of my machines!
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Good Stuff here. Thank you for the tip. Works great.
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Love this – the way they told me about their change here in DC by telling me I have a virus. Nice…
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Thank you so much for the solution. I thought there for a second there was something wrong with the data I inputted into my program so I did a search on the web for the info and I came here.
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What happens when you set it up this way and take your laptop on the road? Will you still be able to use the comcast server on 587 from a hotel?
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Have any of you filed a complaint with the FCC? Nothing will get changed until the people with the big hammer are notified. The FCC is already investigating Comcast and have found them lacking. Now’s the time to make your displeasure known.
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Bastards. If they are right, and I was sending spam via a bot, then this is the first recorded occurrence of such a bot on a Mac. I don’t buy it. I think they’re just running a crappy service.
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Thanks for the instructions; that fixed my problem. I hadn’t been able to send mail all week and couldn’t figure out why.
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thanks for the help but this still hasn’t fixed my issue with comcrap email. i called their tech support which was as useless as they come. the guy was trying to tell me my outlook was setup wrong. funny how it’s been working with SSL for a couple years now and just stopped.
i just tried to call 856-317-7272 so apparently they know about it because the automated system said if u r a comcast customer press 1, if u r having email issues press 1, if you can not send email press 1, we r now closed. grrrrr comcrap
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One more step may be needed. I had the identical problem, which also was resolved by calling the security department (after hours of nonsense from other personnel, including ” we don’t allow customers to send email with their own domain any more”. I use Eudora 6.2 with Max OSX 10.4.x, comcast, netgear hardwire/wireless combo router. The router is firewalled.
The comcast security 888-565-4329 said they would lift this one time only, even though there was no evidence of any problem with any of my domains.
They required: – firewalled router (yes), port 587 (some other options too, as long as it’s not port 25) which I had checked as yes, and smtp authentication- yes.
I was still getting an error in eudora though. This was fixed by going to my cpanel where I host my domains, and adding port 587 to the web host manager. see http://webmastersedge.net/home/2008/cpanel-tutorial-opening-up-another-port-for-smtp-when-port-25-is-being-blocked-by-your-isp/ for additional information about Setting Up Exim To Listen On Your Chosen Port.
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The fix worked for me.. Thanks
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This fix worked for us too. Comcast is horrible, wish there were alternatives in our area. THANK YOU
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Thank you
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Thanks for posting this – I have just been having this problem over the past week. Your suggestions fixed everything!
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I,ve been fighting this for two friggin weeks – it worked on port 25 one day then poof! I made the port change and allow authentication. Works fine. BTW my iMac MAIL was okay.
Pragmatic JIM
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Yep scumcast got me with this a few weeks ago. I’d been using the same email config for almost 3 years without any problems and then suddenly *poof* can’t send email. Had an interesting conversation with their helpdesk where the oper insisted that I couldn’t have been using port 25 and that the server I was connecting to at my workplace didn’t use that port. Even after I informed him that I was the person that built it……..
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3 tech reps later & I end up at Microsoft Outlook Express drooling for $49.00 which they won’t charge if they can’t fix it. Well, guess what, it’s not Outlook – it’s Comcast & the morons at Comcast can’t fix it… Ad I thought I was heading up the ladder to a higher tech ground, all of a sudden I was speaking to a Microsoft office in India… Great world we live in. Still can’t send out mail thru my company server.
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Thank you for your help.
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Thanks this worked for me, BTW I had to add one thing since I am using comcast’s smtp for other mail addresses I had to added my comcast authentication info too.
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They (Comcast) screwed me as well. My company laptop is setup through our company ISP and that email account uses port 25. They wouldn’t release it for me, and now I have to contact my company ISP and try to get another port. I hope no friends or family ever want to email from my house via wireless. I don’t fell I’m getting 100% internet service anymore, I may stop paying 100% of the bill.
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I recently had my port 25 blocked. My wife and I are not spammers, and now we cannot use our Apple Mail to check our email. This recently happened to a friend of mine as well. It appears the blocks are random, as the Comcast Support explicitly told me there is no block on my port 25. I am in the process of contacting the local news to report this incident and make Comcast’s unjust policies known.
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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 talked about Comcast selecting certain modems and blocking Port 25 that way.
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The comcast tech was an idiot. I tried asking them why this happened all a sudden, explaining I was concerned because that I read in a forum that maybe comcast detected an email worm that was sending out a bunch of mail via smtp and could this be why they suddenly started blocking?
He proceeded to explain to me that’s impossible because comcast only supplies the internet mail servers, they don’t control outlook express, that’s not their product that’s a Microsoft product. WTF? That has nothing to do with it and I tried explaining that to no avail.
I spent hours, like 4 hours, at my mom’s trying to figure this out. We both use comcast and I can still use port 25 fine so I first assumed it was a problem on her end so I didn’t call them up right away — first I disabled then tried uninstalled firewalls, virus scanner, using different email client… even tried port 587 per a forum suggestion. Turns out that I also needed to turn on smtp authentication to send email in addition to port 587.
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Ah, tech support problems. But, Pete, what’s with the surprising need for authentication? As soon as you switched the port, your mail client should have reported the server error that’s pretty clear about needing authentication. If your client doesn’t show you server errors, get a better client :-). (I use Thunderbird.)
Anyway, thanks for the info, this is what I needed to get mail working again. smtp.comcast.net blocks ICMP and, at least for my IP, shows port 25 as “filtered” but 587 is “open” (hurray for nmap!). All I needed was that magic number and I had things working again in under a minute.
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After reading all of the above and changing from 25 to 587 I am still unable to send mail. Using Windows Mail with Vista Ulitmoate x64 with comcast wireless internet.Any suggestions. Thank you.
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After a short talk with abuse department of Comcast, they unblocked the port 25. Microsoft Mail is sending mail now.
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Thanks for the help! Lost half a days work before I figured out what was wrong from this post. Quick call to abuse and they figured it out, I had to use port 465 instead.
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I too use IX Web hosting and when i talked with them they would NOT unblock. What did you say to get them to unblock?
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anyone can make a complaint about your IP address…and it is standard practice for comcast to switch your SMTP to 587 so they can spy on it. I don’t think it’s legal if you own the modem…I’m looking into it.
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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?
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Thanks! This just effected me in Chicago and now I’m set thanks to your post.
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Thanks – this was the first hit I got when I googled the problem I was having, and it worked like a charm. Sometimes I love the web.
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I was directed to the abuse support at comcast and was directed to this oneclick fix and it worked. Why the level 2 support couldn’t tell me about this I don’t know
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Here is the link, I was so happy I forgot to include it!
http://www.comcastsupport.com/OneClickFix/autosolutions2alternateports.asp
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Thanks. This fixed me.
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I had Concast with a Scientific Atlanta Modem and could not receive e-mail from bellsouth account I was going to migrate from but my DSL modem worked fine. Furthermore my modem would loose the connection after the next DHCP lease (Every hour) and not recover unless I connected through the PC. Also could not maintain a VPN connection for more than an hour for the smae DHCP lease problem. Comcast says they will not change the hourly lease, that my program (Outlook) is at fault for the e-mail problem (even though it works with DSL) and they do not block Routers. Lies…Lies….Lies
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I am another of those who was blocked by Comcast a few years ago and have found a simple solution to the problem you might want to pass along on your blog.
In Outlook and I would think Thunderbird simply change (I use OUTLOOK) E-mail address to anything other than the address they are blocking. If you are using say joe@carshow.com in that field simply change that to joe@cars.com
Once you do that run the Test Account Settings, once that completes check your mail. As you will see you are once again able to use SMTP email using your own @domain.
What I’ve discovered is that Comcrap has basically blocked anyone and everyone from sending email using their servers once anything using your email name sends spam. Whether you did or not. I would say 95% of the people are not doing this. Someone has spoofed their addy causing the problem. Comcast does not care who sent it, they simply ban you from sending mail through their servers. In my opinion Comcast does not want to actually stop spammers by actively cutting them off. Instead they take the easy route and just ban everyone. The cheap way out.
Interestingly enough I have found that some ISP’s are filtering/looking at one item when you send mail via SMTP (Comcast) and that item is the E- Mail Address. Kind of lame but this would be typical of comcast’s bandaid fix to a much larger problem caused by actual spammer’s (who are making a lot of money using our emails addy’s) and not their customers.
The only effect that you see if you make the change I suggest is in your email header that a person receives. In the From: you will see it as Joe [joe@cars.com] instead of Joe [joe@carshow.com]. Your reply address will be the correct (your domain) address if someone hits reply.
At any rate this is a work around that works for those who need to send SMTP using their own domain address that comcast/other ISP may have blocked.
Of course the Port 25 issue is one that Comcast put into use a few years ago, moving to Port 587 solves that problem.
All in all this kind of crap is typical of ISP’s who are making billions and are to cheap to actually fix the real problem.
Hope this helps some of you.
Jim
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We have just had this begin 3 weeks ago – I have been fighting with Comcast regarding blocking to no avail. Every machine I hook up to the smtp.comcast.net mail server shows that mail has been sent – but it simply disappears – never received by anyone.
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Forgot to add: We can take our machines to Starbucks – use our own domain to send the mail out and it works like a charm. This is definitely a comcast issue
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Interesting thing!
This is my first time comment at your blog.
Good recommended website.
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Thanks for this blog. This shows why public utilities need to be regulated. Unfortunately, the FCC is way behind the curve… or maybe in Comcast’s pocket?
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Thank you so much for posting the port 587 solution! I am a comcast customer and I couldn’t send e-mails from Outlook 2007 when I was visiting my family (who’s ISP is Verizon). I can send mail now!!!!! Thanks again!!!!
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