Note: many clients (e.g., Thunderbird) let you configure only one incoming and one outgoing server.
Recommended (STARTTLS test, paper-default):
IMAP: host selftest.nsipmail.de, port 143, security STARTTLS
SMTP (submission): host selftest.nsipmail.de, port 587, security STARTTLS
Optional (implicit TLS variant):
IMAPS: host selftest.nsipmail.de, port 993, security SSL/TLS
SMTPS: host selftest.nsipmail.de, port 465, security SSL/TLS
Optional: SMTP host selftest.nsipmail.de, port 25, security STARTTLS (some clients don't use this)
Use autodetect by entering the email address test-JfFXlgowf4@selftest.nsipmail.de in your client.
This relies on DNS SRV records (no XML). Client support varies.
_imaps._tcp.selftest.nsipmail.de PRI 0 WEIGHT 1 PORT 993 TARGET selftest.nsipmail.de.
_imap._tcp.selftest.nsipmail.de PRI 0 WEIGHT 1 PORT 143 TARGET selftest.nsipmail.de.
_submissions._tcp.selftest.nsipmail.de PRI 0 WEIGHT 1 PORT 465 TARGET selftest.nsipmail.de.
_submission._tcp.selftest.nsipmail.de PRI 0 WEIGHT 1 PORT 587 TARGET selftest.nsipmail.de.
_smtp._tcp.selftest.nsipmail.de PRI 0 WEIGHT 1 PORT 25 TARGET selftest.nsipmail.de.