Complete procedures with a way back.

Combine SMTP, submission, virtual domains, Dovecot authentication, LMTP delivery, IMAP TLS, quotas, Rspamd, DKIM, DNS, backups, and end-to-end validation.

Set canonical identity, destinations, trusted networks, relay restrictions, DNS, TLS, aliases, logging, and end-to-end tests without becoming an open relay.

Install Rspamd, use local milter sockets, define fail behavior, train no data implicitly, add DKIM keys and DNS, tune actions, and test inbound and outbound paths.

Set relayhost, authenticate with a protected map, require verified TLS, scope sender rewriting, preserve local delivery, and test deferral on outage.

Add a dedicated submission service, require STARTTLS and SASL, integrate Dovecot authentication, constrain relaying and abuse, and test safe failure modes.

Separate hosted domains from local identities, create deterministic mailbox and alias maps, validate catch-all behavior, integrate delivery transport, and test unknown recipients.