Glossary
Envelope Sender (MAIL FROM)
The envelope sender is the address in the SMTP MAIL FROM command — also called Return-Path or bounce address. It is separate from the visible From: header. SPF validates against the envelope domain — DMARC alignment requires envelope domain to match From: for SPF alignment.
Why it confuses people
Users only see From: — receivers see both. Misalignment is invisible in the inbox until DMARC fails.
FAQ
Where do I see envelope sender?
In raw headers as Return-Path — often after delivery.
Can envelope and From differ?
Yes — common for ESPs — that’s why DKIM alignment matters.
Does SRS change the envelope?
Yes — forwarding can rewrite envelope for deliverability.