backup.example.net
← All inbound domainsDNS status error
Cached a few minutes — use Re-check after publishing. Unlike outbound, inbound needs an MX pointing at this server.
No MX points at mail.example.org (this server). Publish the record below, or wait for DNS to propagate and Re-check.
Upstream
Where accepted mail is handed off. Not a mailbox.
MX record to publish
Add this MX so the internet delivers here. Keep any existing primary MX if this is backup-MX.
Valid recipients
Who this domain accepts on port 25. Same idea as an application’s address mode: a list, or any address at the domain.
Unknown recipients are rejected at RCPT so this relay does not generate backscatter.
Every address at this domain is accepted and forwarded. Prefer a list unless the upstream rejects unknowns — otherwise this relay may generate backscatter.
Danger zone
Stops accepting mail for this domain. Does not touch outbound sending domains.