Is 421 4.7.32 permanent or temporary?

421 4.7.32 is a temporary (4.x.x) failure — a properly configured mail server retries automatically, and the message often delivers on a later attempt. Persistent 421 4.7.32 across recipients points to a deeper issue.

Is this my problem or the recipient's?

Often it resolves itself on retry. If it persists across many recipients, it's usually a sending-side reputation or authentication issue worth fixing.

How do I check my sending setup?

Run a free EmailHealth check on your domain — it verifies SPF, DKIM, DMARC, blacklist status, and more in a couple of seconds, which covers the most common causes of delivery failures.

421 4.7.32 — Gmail: From: header not aligned with SPF or DKIM

421 4.7.32 is a temporary SMTP reply meaning gmail: from: header not aligned with spf or dkim. SPF or DKIM may pass, but for a different domain (for example the ESP's own domain). DMARC needs one of them to pass for the From: domain itself. That is called alignment.

What 421 4.7.32 means

SPF or DKIM may pass, but for a different domain (for example the ESP's own domain). DMARC needs one of them to pass for the From: domain itself. That is called alignment.

ℹ️

This is a 4.x.x temporary failure — a correctly configured mail server retries on a backoff schedule, and the message frequently delivers on a later attempt.

Common causes

📨

The ESP signs DKIM with its own domain

Most common

Mail is signed d=sendgrid.net or d=mailchimpapp.net instead of your domain, so DKIM is not aligned.

🔁

The Return-Path uses the ESP's domain

Most common

SPF passes for the ESP's bounce domain, not for yours, so SPF is not aligned.

⚙️

You send as a domain you have not set up

Common

The From: uses a brand or secondary domain that has no DKIM or custom return path.

How to fix 421 4.7.32

1
Set up domain authentication in the ESP
Most platforms call this "domain authentication" or "custom DKIM". It makes DKIM sign with d=yourdomain.
2
Add a custom return path
A CNAME such as bounce.yourdomain makes SPF align with your From: domain.
3
Confirm alignment
Send a test message and check that dkim=pass header.d= or smtp.mailfrom= shows your own domain.

Confirm your domain is set up correctly

Most delivery failures — permanent or temporary — trace back to authentication or reputation. Run a free EmailHealth check to confirm SPF, DKIM, DMARC, blacklist status, and TLS are all healthy for your sending domain. If you send in volume, free daily monitoring will alert you before a small issue becomes a flood of bounces.

Gmail: From: header not aligned with SPF or DKIM