Deliverability glossary · Updated 2026-08-10
MAIL FROM domain
Also called: Envelope sender, Return-Path
The MAIL FROM domain is the address in the SMTP envelope that receives bounces. Setting it to a subdomain you own — rather than your provider’s domain — is what makes SPF align for DMARC.
Every message has two senders: the one the recipient sees in the From header, and the envelope sender used by the mail transport. The envelope sender is where bounces go, and it is the identity SPF actually checks.
By default many sending platforms leave the envelope on their own domain. Mail still delivers, but SPF passes for the provider rather than for you, so the SPF leg of DMARC does not align. You are then relying entirely on DKIM for DMARC to pass.
Configuring a custom MAIL FROM — typically something like `mail.send.yourdomain.com` — moves the bounce path onto your domain. It requires an MX record so bounce mail can be delivered, and an SPF record authorising the provider. Both must exist or the configuration fails.
The payoff is a second independent path to DMARC alignment plus bounce data attributed to your domain rather than pooled with every other customer of your provider.
How Raechly handles it
The MAIL FROM subdomain is configured by default, not as an advanced toggle. Its MX and SPF records are part of the DNS set `create_domain` returns.
Related terms
SPF record
An SPF record is a DNS TXT record listing which servers are allowed to send mail for your domain.
DMARC
DMARC is a DNS policy that tells receivers what to do when a message fails SPF and DKIM alignment: nothing, quarantine it, or reject it.
Hard bounce
A hard bounce is a permanent delivery failure — the address does not exist or the domain rejects it outright.
Back to the full deliverability glossary, or read how these pieces fit together in how Raechly protects deliverability.