Please verify your settings with following ones:
1) Username: <user>@domain.com
2) Password: password for the mail box that you are configuring
3) POP3 (Port 110) : "mail.domain.com " without SSL\TSL.
OR IMAP (Port 143): "mail.domain.com " without SSL\TSL.
4) SMTP (Port 25 or 587) : "mail.domain.com " without SSL\TSL.
Also, please make sure that there is enabled the authentication for SMTP and there is used normal password authentication type for it, without TSL\SSL or SPA.