I setup Postfix and Dovecot on a new Ubuntu box following these directions.
From a client machine, I validate that POP3 seems to be working
telnet mydomain.com 110
+OK Dovecot ready.
USER me@mydomain.com
+OK
PASS mypassword
+OK Logged in.
quit
+OK Logging out.
However, when trying to configure Gmail on the same client to retrieve email via POP3, I get the error
Server denied POP3 access for the given username and password.
Server returned error: "Login failed."
I carefully confirmed that Gmail is configured to use the same POP Server, Port, Username and Password I used when checking the connection with telnet.
What could be causing Gmail to get a "Login failed" message?
Best Answer
It turns out that, while DNS changes to point to the new server had propagated to my local box when I did the testing, they had probably not yet propagated to Google.
Retrying the procedure the following day worked just fine.