Spam filtering

Rspamd analyses mail and can apply scoring, rejection, temporary rejection or other configured policy actions.

Greylisting

Temporary SMTP rejection can be used as an anti-abuse mechanism. Legitimate standards-compliant mail servers normally retry temporary failures.

Authentication security

• Use strong unique mailbox passwords.
• Disable abandoned accounts.
• Use encrypted submission and mailbox access.
• Protect administrative credentials separately from mailbox credentials.

Network exposure

Expose only the mail services required by the deployment. Supporting databases, cache services and private administrative interfaces should not be unnecessarily Internet-accessible.

Abuse response

Monitor repeated authentication failures, suspicious sending behaviour, unusual queue growth and abnormal spam-filter events.