I set up Google apps email with my Mac Mail client. It worked fine until I tried to send email from within the client. I couldn’t find too much info about it online, and went a couple of months sending (annoyingly) from the gmail web interface. This was annoying, so thought I’d finally go about fixing it once and for all.
Here’s what worked for me
So to reiterate my specific case, I could receive email, but couldn’t send it. Here’s something to try:
1) Find the “edit SMTP server list” options panel:
2) Make sure that your User Name and password fields are correct, that “Use default ports (25, 465, 587) is checked, and that you’re using SSL.
My problem was the for some reason Mac Mail had decided to change the SMTP server user name to just “joe” instead of “joe@mydomain”.
Useful links in case this doesn’t solve it for you: