For IMAP account settings:
Incoming port should be set to 143.
Outgoing port should be set to 587.
Make sure that SMTP Authentication is checked.
SSL should also be set to OFF.
For POP3, which we discourage:
Incoming mail records should be set to port 110 and outgoing mail record settings should be set to port 587.
Please uncheck the box to leave a copy of the message on the server. This can cause duplicated emails.