Tools > Email Account > Add a new E-Mail account > IMAP
Enter "Your Name"
Enter "Your E-Mail Address"
Incoming IMAP server "mail.yourdomain.com"
Outgoing IMAP server "mail.yourdomain.com"
Enter "your username"
Enter your Email password
Click "Remember Password"
More Setting > Outgoing Server
Check "My outgoing server (SMTP) requires authentication"