← Glossary
Authentication
What is Return-Path (envelope sender)?
The address bounces are sent to, set during the SMTP conversation, and the domain SPF is checked against.
How it works in practice
It's separate from the From address people see. Sending platforms usually set the Return-Path to their own bounce domain, so SPF passes for the platform's domain rather than yours. A custom return-path domain on your own domain fixes the alignment.
The common mistake
Ignoring the Return-Path domain and then wondering why SPF alignment fails.
Related terms
Not sure whether this is what's hurting your inbox placement? A free deliverability review finds the real cause.
How we help: Consulting · Private infrastructure · Managed mailboxes · Monthly support