by rob » Mon Jul 13, 2009 12:19 pm
It would appear I misread your original post. Your laptop is the one that works fine and its the other computers that have an issue. The problem could simply be that your other computers are not authenticating correctly and so not gaining relaying permissions, either by a setup mistake or due to a firewall/router. To send mail locally only you of course dont need to authenticate, but the SPF records will be enabled (you can verify this by checkign the logs to see if the connection attempts to send the mail are authenticated). I recommend ensuring that SMTP Authentication is enabled in your SMTP relaying settings on the mail server, then verify each mail client is setup to use this. If you find that some clients are having problems while this is enabled, then I would check the logs to see if the client ever tries to authneticate.