Return-Path and Envelope Sender Explained

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.

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.