Shaw cable. They are one of our ISP’s that provide cable internet access. I have used them for about 10 years and they are pretty good, BUT they seem to have a problem with updating customers and letting them know when changes have been made to their system, which is the case I was faced with yesterday when I could not send any private domain mail from my desktop mail client, being Office Outlook. I also tried using Mozilla Thunderbird with the same issue. An error was returning that an internal server error had occurred. Now, for this error, when I write private domains, they are domains I own that I have set up a pop email account for. This did not however affect my shaw email account. So to clarify. firstname.lastname@example.org was not sending, where email@example.com was. So I suspected initially, Ensim on my server was misbehaving.
First thing I did was restart the bind and ensim services on the server, which didn’t correct the problem, then I tried updating the server software, still, no fix. Finally, I tried setting SMTP to a different port because Shaw uses port 110 for receiving mail, blocking port 25.
So what I did is add port 26 to my SMTP configeration on the server, and change my SMTP settings in Outlook to the same port and ran a test email.
Therefore, effective March 16, 2011, Shaw Cable is no longer allowing SMTP connections for private domains on port 25. Unless you are a system admin, familar with adding ports for SMTP, open a support ticket with your host and explain that your ISP is blocking port connections to Port 25, and you would like Port 26 added to the SMTP configeration. This is done to ‘supposedly’ cut down on spam send through your ISP. However, if customers must search for solutions, spammers can as well 🙂