What Is the Return-Path#
Every email has two "From" addresses:
- Header From (
From:) — the address your subscribers see in their mail client.
- Envelope Sender (also called MAIL FROM or Return-Path) — the address used during the SMTP conversation, where bounces are delivered.
These can be different, and that difference matters for both bounce handling and DMARC alignment.
The SMTP Conversation#
During delivery, the sending server opens an SMTP connection and states:
MAIL FROM: <bounces@mail.yourdomain.com>
RCPT TO: <subscriber@gmail.com>
DATA
From: Your Brand <hello@yourdomain.com>
Subject: ...
The MAIL FROM is the envelope sender. Gmail will set the Return-Path: header in the delivered message to this address.
Why It Matters for DMARC#
SPF checks the envelope sender domain (Return-Path), not the From header. For SPF alignment in DMARC, the Return-Path domain must match the From domain.
| Scenario |
SPF Check |
DMARC Alignment |
| Return-Path = yourdomain.com |
Pass |
Aligned |
| Return-Path = sendgrid.net |
Pass (for SendGrid) |
Not aligned |
| No SPF record on Return-Path domain |
Fail |
Fail |
Configuring Return-Path in AcelleMail#
Under Settings → Sending Domains, enable Custom Return-Path and set a subdomain like bounce.yourdomain.com. Add the required SPF record for that subdomain. This ensures DMARC SPF alignment and routes all bounces to AcelleMail's handler automatically.
