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 email@example.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?