The hidden envelope address bounces go to. A custom return-path on your own subdomain aligns SPF and keeps “mailed-by” on your brand.
It’s a different header from the visible From — the distinction matters for both deliverability and threading, covered in Reply-To vs From.
Envelope vs header sender
Every email carries two senders. The header From is what a recipient reads. The return-path — the envelope MAIL FROM set during the SMTP handshake — is where the receiving server sends bounces and where most mailbox providers check SPF alignment. They can differ, and when a third party sends on your behalf the return-path often points at the sender’s domain, not yours.
Why it matters
- SPF alignment. SPF authenticates against the return-path domain, so a custom return-path on your own subdomain lets you pass aligned SPF instead of borrowing the provider’s.
- “mailed-by” on your brand. Inbox clients surface the return-path domain as “mailed-by.” On a custom one, that line reads as your domain rather than a vendor’s.
- Bounce handling. Bounces return to the return-path. Owning it means your sender — not a shared third party — sees and acts on hard bounces and complaints.
How a custom return-path works
You delegate a subdomain (often something like bounces.yourdomain.com) by adding the DNS records your provider specifies. Outgoing mail then uses that subdomain as the envelope sender, SPF is published there, and alignment holds. Pairing it with DKIM signed by your domain gives you aligned SPF and DKIM, which is what DMARC evaluates. For a worked example, an e-commerce store moving off a shared sending domain typically sets up the subdomain, watches “mailed-by” flip to its own brand, and sees fewer transactional receipts land in spam. The full setup is in the deliverability guide.
How Cherryrise handles it
Cherryrise signs outbound mail with your own DKIM key (BYODKIM) and supports a custom return-path subdomain, so SPF and DKIM both align to your domain and “mailed-by” shows your brand rather than a shared sender. Bounces and complaints route back to your own infrastructure, where they feed suppression. See email deliverability for the full picture.