Apache James Server is configured by default to avoid being an SMTP open-relay.
SMTP Auth and "Verify Identity" options are enabled when you install James (read more).
Apache James Server supports SSL/TLS (read more).
Apache James Server supports different user storage (read more) - LDAP support is partail (work in progress).
The Apache James Server version 3.0.0 is vulnerable to Java deserialization issues.
One can use this for privilege escalation.
This issue can be mitigated by:
Read more here.