Before troubleshooting a mailbox configuration issue, note that repeated failed login attempts can cause the public IP address of the device or connection to be blocked temporarily.
If setup has failed several times, confirm the correct settings before testing again.
Check the incoming server, outgoing server, port numbers, encryption type, username format, and password.
Where available, make sure the outgoing server is configured to require authentication.
If the mailbox still cannot connect, collect the full settings being used and compare them against the expected configuration for the account.
