I have had a problem sending emails (via Telia) from my Mac since i upgraded to MountainLion. It turns out that Mail.app have a different setup than previous versions.
As standard. the SMTP settings is set to user default SMTP ports (25, 465, 587) that doesnt work well with Telias SMTP relay server (smtprelay1.telia.com) and iam to lazy to get an telia mailadress to use as smtp-autentication to there regular smtpserver.
When i tried to send an email, i got ”503 wrong state for EHLO command” as a result in the mail-log.
It turns out theres an easy fix, by luck i tried pressing the ”Custom port” and setting the value to 25 (thats the standard smtp port), and voila, the email was sent successfully!0