Here are the recommended settings for the 1and1 email service.
Note: If you don't know how to set up an email account manually in Postbox, see "Manual Setup" here.
Incoming Email Settings
- User Name — full email address
- Server Name — imap.1and1.com
- Type — IMAP
- Port — 993
- Security — SSL/TLS
Outgoing Email Settings
- Server Name — smtp.1and1.com
- Port — 587
- Security — STARTTLS (if this doesn't work for you, try SSL/TLS)