Okay, mail confusingly has two separate parts. Sending messages, via SMTP or ESMTP. And receiving messages, via POP or IMAP. Sending mail has one set of settings, passwords, host names, etc. Receiving messages and listing messages has a different set of settings, passwords, and host names. Your receiving setting; your POP or IMAP server and/or its settings appear to be incorrect. Here's the general troubleshooting sequence, and you'll want to concentrate on the POP or IMAP settings. These (sending and receiving) settings are unfortunately unique to each email provider in existence, which means we'll either need to know the provider to look up the details for you, or you may have to check directly with the provider support folks directly for some of the lesser-known and private providers.