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One Postfix to route them all: self-hosted multi-tenant mail delivery
January 2026 — on getting email routing right when you have more than one domain
Most self-hosted email guides start with a single domain. Install Mailu or Mailcow, point MX at your server, done. That works well until you have multiple domains that need to receive mail, or you’re providing mail routing for several distinct tenants, or you want a single SMTP gateway that routes inbound mail to different downstream servers based on recipient domain.