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 mailhost.worldnet.att.net
Comcast: Use Port 587 or set your outgoing SMTP to smtp.comcast.net
AOL : outgoing mail server to smtp.aol.com
NetZero: outgoing mail server to smtp.netzero.net
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 comcast.net 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.”