Can’t send SMTP Email?

If you are having problems sending email using your own mailserver, make sure that your ISP has not blocked your domain’s IP or SMTP port 25. Recently, Comcast has done just that. I’ve had a flurry of issues and have had to make changes to my client’s outgoing settings in their Outlook.

There are various solutions to consider:

As an example,  WestHost will setup an alternate port (2525 versus 25). Then you would need to set your Outlook to send email on port 2525 and to authenticate to the outgoing server, using the same information as the incoming server.

Each host will have their settings or you can use the server settings that your ISP provides you. Below are various SMTP settings for top ISPs. You will need your ISP login and password if you decide to use their outgoing SMTP.

AT&T: Set your outgoing SMTP to
Comcast: Use Port 587 or set your outgoing SMTP to
AOL :  outgoing mail server to
NetZero: outgoing mail server to

Below is Comcast’s Explanation:

“Port 25 is an unsecured port on a computer that those sending spam can take control of to send spam – often without the user ever knowing his/her computer has been compromised. When spam from a compromised computer is detected, Comcast’s anti-spam systems automatically apply a sending block and send an email notification to the affected subscriber’s email address. This block does not interrupt mail service for Webmail (e.g. Comcast, Yahoo, Gmail, or Hotmail); however, this block does prevent email programs or clients (e.g. Outlook Express) from sending email. Client e-mail programs will still receive email. The instructions at our mail client help page explain how to configure common email client programs to use Port 587, which includes authentication, instead of Port 25.”

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Christina Hawkins

Since 1999, Christina has been designing and building exceptional websites. With many years of experience in creating thousands of websites, she understands the need for continuing education in her field and, therefore, is constantly learning and teaching others about internet marketing and digital processes. Christina is known for her highly-collaborative methods that help her realize the vision each customer has to successfully create engaging content to captivate targeted audiences across multiple platforms. Christina has honed her digital marketing and graphic design skills so that she can help B2B industries get their message out to their target audience in the right way. In addition to her ability as a digital marketer, Christina serves as a coach and mentor with WPElevation to other digital marketing freelancers, helping them grow their businesses. She is also a sponsor and co-leader of Houston's WordPress Meetup.


  1. SearchNetMedia on October 16, 2009 at 8:47 pm

    Thanks for the info. This was a real frustration today, but we got it solved. I would like to add something. Comcast gave us a new password and said “they reset the account”. This along with what you describe above change from Port 25 to Port 587 for the outgoing server is also important (thanks to ComcastGeorge) on twitter. If you are using a non-comcast email address and your own domain…and your incoming is say [email protected] (and using your own user name and password) for incoming servers, you still need to check “my server needs authentification” under the Outgoing Mail Server under the Server tab in Account (mail) – Properties. Then, next to that checked box to the right is SETTINGS button. click that and put in your comcast user name and password. Then it worked. So, in summary you need a user name and password for the incoming server (if using a non-comcast email address), and another user name and password (your Comcast ones) for the Outgoing Mail Server.

    The last two year you could just send outgoing mail through without authenticating, but it appears no more. We were told by Comcast early in the day that it was a Microsoft Outlook Express problem. We downloaded Mozilla Thunderbird (which is like Outlook Express) and we had the same problem there. It appears that Comcast Engineering changed this outgoing mail process and forgot to tell Customer Support.

    • admin on October 19, 2009 at 3:12 pm

      Hi searchnetmedia. I appreciate the comment and follow-up. It’s been a struggle as each ISP changes its SMTP policy. Then to add to the problem, they almost hide their smtp information deep in their support pages.

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