When sending emails with PHP, (from looking at the logs) the from address is translated to 'webIDemail@example.com. But when the email is delivered, the from address looks correct (mailbox@domain). So here is the example from my log: amavis: (02564-02) Passed CLEAN, <firstname.lastname@example.org> -> <sales@recipientdomain>, Message-ID: <20090331122742.9E66FF7C24F@websrv1.serverdomain> So the server domain is not the same as the website sending the email. I can't even see a reference of the actual domain. some mail servers will not accept emails like this. said: 550-Verification failed for <email@example.com> 550-The mail server could not deliver mail to firstname.lastname@example.org But if it did a verification on the actual sender domain, it would be fine. When using Outlook, it does not do this. The address is correct, even when looking at the log. I had the same thing with ISPconfig2, just cant figure out what it is. Any help would be much appreciated.