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SMTP outbound blocked


SMTP outbound blocked

Got U-Verse + Internet.  Specifically asked if it was ok to run my own e-mail server (sendmail: personal use, personal domain, no hosted, no relay).  Was assured it was fine to do so, and that AT&T would setup my DNS PTR record for my static IPs.


Had to call in to remove the block on outbound SMTP (tcp 25).  They removed it, no problems for months.


Recently lost connectivity all day, think nov 2nd.  Outbound SMTP has been blocked again since.  Obviously an AT&T network problem.  "telnet <remote MX> 25" times out.  tcptraceroute dies at the AT&T 2wire router.  Remote mailservers never see any traffic from me when doing a packet capture on them.  My own equipment has been testing without any firewall at all beyond the at&t provided 2wire modem/router.


Uverse tech support level 2 tells me that outbound SMTP is not blocked, and that I should call Connect Tech.

Connect Tech tells me that it's an obvious network problem and I should call DSL tech support.

They refer me back to connect tech, who refers me back to tech support.  Over and over... all darn day.


What can I do?  I can't get anyone to escalate this issue to anyone that even knows what "SMTP" is.  I've had people try to walk me through setting up 'the outlook' (*sigh*... I don't even use windows let alone 'the outlook').  I had one tech insist that I *HAD* to use Yahoo webmail and that makes port 25 work.  (Really?)


So frustrated.


I know my stuff, I'm a high-end Linux and Network guy by trade.

I know AT&T is still blocking SMTP out.  I can't seem to convince anyone of this and just get the constant ping-pong between dsl tech and connectech.


There's just GOT to be some way to get this escalated beyond all these low-end call center reps.  Suggestions?  Anyone have a magic phrase that gets you past the connect-tech <--> dsl support loop?


Message 1 of 67

Re: SMTP outbound blocked

Matt, from U-verse Care, just told me that there is a $29 fee to unblock the port when I emailed this afternoon, and that didn't sound like everything else I was reading.  I guess I'll try again.

Message 16 of 67

Re: SMTP outbound blocked

Matt is usually really on top of things.  If there is indeed a $29 fee to unblock port 25, that is a newly instated charge.


Message 17 of 67

Re: SMTP outbound blocked

I have been trying to set up my office email on Outlook 2010 with Windows 7 on IMAP since last one week! I got help from our office IT guy . He tried POP# also but did not work. On IMAP I receive my office emails but cannot send out any. Our IT person said AT&T must be blocking the outgoing SMTP due to spam problems. Instead of yahoo servers he used our office servers both for Incoming & Outgoing servers. For Incoming & Outgoing ports he tried various combinations including Incoming of 110 and Outgoing 587 (as well as 25). I talked to ATT support by phone and by chat and they keep on referring me to their paid tech support! Please advise. Thanks in advance! Ray 

Message 18 of 67

Re: SMTP outbound blocked

The port 25 outbound block really shouldn't bug that many people.  Using SMTPS (SSL/TLS) is FAR preferred.


For client-to-server communications, simply checking the box or dropdown or whatever in outlook to use SSL or TLS for SMTP would fix it handily if your mail server is setup to handle SMTPS on 465 or 587 - without the need to unblock port 25.  So if that didn't fix it either your server doesn't accept SMTPS or you've got a bigger issue.


AT&T only blocks outbound 25, and a simple call or chat to tech support will unblock it for free.  (My case was special as something with my account provisioning was goofed up - BUT the initial unblock of outbound port 25 worked and was handled quickly... and freely)


Just say, "I need port 25 outbound unblocked".


Here's how you can test...

(Forgive me, I'm not a windows guy, so this may not be exact)


First, since you're running windows 7, install telnet.

  1. Start
  2. Control Panel
  3. Programs And Features
  4. Turn Windows features on or off
  5. Check Telnet Client
  6. Hit OK

Then fire up a command window.  Either powershell or cmd is fine.  Hit windowskey+r for a run prompt and type in "cmd", hit enter or OK.  Should see the black command prompt box.


At the command line, type in "telnet <your outbound/smtp mail server> 25".

You should almost immeadiately get a blank screen... maybe a banner along the lines of "220 ESMTP...".  Typing 'quit' and hitting enter should return you to the normal C:\whatever prompt.  Should be very quick.

If it just sits there with "trying 25..." for a long time and finally fails with connection timed out... then port 25 outbound is blocked.

Test against another mailserver as well. is a good test - it accepts SMTP via 25, 465, and 587.

You should also test telnet to 587 to your mailserver to ensure that works at least.  If so... again... checking SSL for SMTP servers should work just fine.  AND it's far preferred to use SSL anyways!!!


Of course, disable any software firewall you have on your machine, and try again.  The basic Windows firewall will mess with you as well I'd imagine - again, not a windows guy, but you can disable that thing too.

Don't leave the firewall disabled.  If that's the problem - you need help configuring your software firewall, and I'm not the guy to help with that.  I'm more of a server/network guy... don't even use windows if I can help it.  But I'm sure no matter what software firewall you're using you can allow SMTP and SMTPS in it.


Anyway, testing that stuff lets you know where you stand.  Testing beyond that gets pretty in-depth as you can see from my earlier posts.  I went as far as doing packet captures on both ends and testing many many mailservers.  But again... my problem was very abnormal.


Message 19 of 67

Re: SMTP outbound blocked

I'm having a similar issue but slightly different (I think). I'm new to networking and all so please point me in the right direction.

I recently registered a domain name and want to host my e-mail services on my computer at home so I changed the A and MX records to have traffic sent to my IP address assigned by ATT. I have Uverse. I downloaded hmailserver and configured it correctly (I think) and set up a few accounts.

I sent an e-mail from my gmail account to the new e-mail I just set up and didn't get a bounceback. However, my server doesn't seem to get the e-mail.

When I ran the "diagnostics" on the server admin and it seems both inbound and outbound traffic on 25 passes through. This is what I get:



  1. Test: Collect server details
  2. hMailServer version: hMailServer 5.3.3-B1879
  3. Database type: MySQL
  4. Test: Test IPv6
  5. IPv6 support is available in operating system.
  6. Test: Test outbound port
  7. SMTP relayer not in use. Attempting
  8. Trying to connect to host
  9. Trying to connect to TCP/IP address on port 25.
  10. Connected successfully.
  11. Test: Test MX records
  12. Trying to resolve MX records for hostname...
  13. Host name found
  14. Test: Test local connect
  15. Connecting to TCP/IP address in MX records for local domain
  16. Trying to connect to host
  17. Trying to connect to TCP/IP address on port 25.
  18. Connected successfully.
  19. Test: Collect server detailshMailServer version: hMailServer 5.3.3-B1879Database type: MySQL
  20. Test: Test IPv6IPv6 support is available in operating system.
  21. Test: Test outbound portSMTP relayer not in use. Attempting to connect to host to connect to TCP/IP address on port 25.Connected successfully.
  22. Test: Test MX recordsTrying to resolve MX records for domain name...Host name found
  23. Test: Test local connectConnecting to TCP/IP address in MX records for local domain...Trying to connect to host...Trying to connect to TCP/IP address on port 25.Connected successfully.



Message 20 of 67

Re: SMTP outbound blocked

I thought I'd throw in my experience with this since this is the thread that helped me get my similar problem resolved. I at first called U-Verse technical support where after about 12 minutes I was disconnected.  I then called back, and their call system clued in on the fact that I still had the problem case open.  I was then connected to a specialist who no matter how I tried to explain that I was trying to setup an e-Mail server kept getting confused and was trying to help me with my e-Mail client configuration.


I then decided to try the chat support.  I connected with a tech and clearly explained that I was trying to setup a linux server and that I'd read that outbound port 25 was blocked.  There were a lot of long pauses, but the tech would look into it and try to open up port 25.  I'm not sure exactly what happened, but then the chat software locked up [I was in Linux/Chrome during the chat session].  I was a little annoyed that I got disconnected.


For kicks then I tried sending a test e-Mail simply using mail from the command line.  Much to my surprise, it worked!  I am now able to send e-Mails from my system[s] without having to worry about trying to authenticate to the AT&T servers with sendmail [such a nightmare configuration wise].


So thanks all in this thread, your advice and insight helped greatly!



Message 21 of 67

Re: SMTP outbound blocked

As a new U-Verse customer, I just went through the Port 25 wars.  It took 43 minutes of waiting and getting transferred and I got hung up on once, but eventually I reached someone who bumped me up to tier 2, who then just.....unblocked it.

Message 22 of 67

Re: SMTP outbound blocked



Thanks for your advise.



Message 23 of 67

Re: SMTP outbound blocked

Tier I is supposed to now have that power; if they sound clueless and try to do the hard-sell (for-pay) ConnecTech, ask to be escalated to Tier II.  Be persistent and tell them you know the score from reading ATT's online forum.  Smiley Wink


I'm not liking how they are using ConnecTech as a solution for TS these days.  What happened to referring customers here?  (Yeah, I know, no $ to be made from U-talk.)


spelling edit

Message 24 of 67

Re: SMTP outbound blocked

I called U-verse technical support and they said that, "due to recent policy changes", they were no longer authorized to unblock port 25 but that I could call ConnectTech and then dispute the charge with Customer Care.  I declined to do that and, honestly, I'm quite annoyed.  If I call ConnectTech, I *would* expect them to charge me a fee and don't want to have to try to dispute that charge.  I looked through the terms and conditions and there is nothing in there about port 25 being blocked.  I require that being open so that I can continue to use an email service that I currently have which does TLS on port 25 for outbound mail, i.e. my outbound mail, from my client to their MTA.


Perhaps a complaint to DPUC will work.  I went from the TS agent to his supervisor and got the same response and I really don't feel like spending hours on the phone over this stupidity.


Anyone have another approach that has worked recently?

Message 25 of 67

Re: SMTP outbound blocked

 Frankly I think it's time for a few complaints to the government. AT&T's arrogance is getting out of hand lately. Maybe it's time the govt steps in again and breaks them up.

Message 26 of 67

Re: SMTP outbound blocked


ram1220 wrote:

 Frankly I think it's time for a few complaints to the government. AT&T's arrogance is getting out of hand lately. Maybe it's time the govt steps in again and breaks them up.

Really, what do you expect that to do?  Our government is about to give the ok for NBC\Comcast merger, do you really think they are going to do anything about how a for profit business carries out it's day to day operations?  If they want you to pay for support, the government isn't going to stop them.  The person on the other end of the phone call probably didn't know what they were talking about and if you ask to be transferred to tier II, the issue will more than likely get resolved.


” Auto racing, bull fighting, and mountain climbing are the only real sports … all others are games.”- Ernest Hemingway
Message 27 of 67

Re: SMTP outbound blocked

Reading this thread was a breath of fresh air. I just got off the phone with DSL tech support (bounced twice to ConnectTech, pointlessly), after trying to explain my problem in technical terms. Its so frustrating when you obviously know more about what you're discussing than the person who is supposed to be helping you, and they get defensive and tell you that you don't.


Anyway, rant over, ... my question is whether David and Matt are appropriate contacts to call for DSL tier 2 support, or are they just for U-Verse? And if not, do you happen to know good level 2 contacts for DSL?




Message 28 of 67

Re: SMTP outbound blocked

David can also handle DSL problems.


Message 29 of 67

Re: SMTP outbound blocked

I have the same problem. I have a personal domain and cannot send over Port 25. I have just spent an exausting 90 minutes being bounced from department to deparment at ATT with people in techincal support that knew less than I did about email services. No one knew Matt or David in Tier II but after speaking to the 6th person I ended up with a VP who actually knew what "SMTP" and "Port 25" were. The short answer is that they will only unblock Port 25 for business customers and not residental and there is not a fee. Regardless, its crazy that it took going through that many people to get the answer. The VP gave me the number to Business Sales to find out what it would cost to upgrade, which was actually for the Residental sales department. I got the correct number for the business side which was an automated system. After going through 2-3 minutes of prompts, I was disconnected. I attempted this 5 more times and had the same problem. After 10 minuntes of getting no where, I called the residental number back, and the guy told me that I need to call 888-757-6500 and just keep pressing 0 until I get to a person. After the joy of verifying my identity for the 10th time today, I was told I need to call 866-620-6000 for small business services. I went through 5 minutes of prompts, and 5 minutes of hold time it tells me the hold time will be 40 minutes and I can schedule a call back. I called back and chose a different prompt and finally got someone on the line.


The shocker, afer ALL THIS is that its not going to cost me any more than I am paying now for residental to convert to a business account. Apparently, it will take a day or two to convert it over and then I can call back and speak to someone about unblocking Port 25. I hope this solves the problem, but my overall experience with ATT was horrible.

Message 30 of 67
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