The Password rejection can confuse people since it's a catch all meaning...
This Password, Username, Authentication method... is not recognized on this Port to this Server.
If WebMail works in a browser, it's not Name or Password, but one of the other ones.
Or Keychain has more than 2 entries for that account one incoming, one outgoing.
The receiving email ports are:
IMAP is port 143
IMAP-SSL is port 993
POP is port 110
POP-SSL is port 995
Outgoing ports are...
SMTP and SMTP-SSL is on ports 25, 587 and 465. Port 587 has to be SSL, and port 465 is enforced TLS-wrapped and is generally used by Outlook users.