Gmail Stopped Warning You in November: Now It's Temporary vs Permanent Rejection. Here's the Difference for Klaviyo Senders

Since February 2024, Gmail has required bulk senders to authenticate, offer one-click unsubscribe and keep spam complaints low. In November 2025 Google began enforcing that more strictly, rejecting a growing share of non-compliant mail instead of just delaying it. A temporary rejection (a 4xx code) means "try again later". A permanent one (a 5xx code) means the message won't be delivered. Knowing which you're getting is the first step to improve email deliverability under the new rules.

Key takeaways

• Gmail's bulk sender rules apply to domains sending roughly 5,000 or more messages a day to Gmail accounts.

• From November 2025, Google ramped up enforcement with both temporary and permanent rejections for non-compliant traffic.

• 4xx codes are temporary and get retried. 5xx codes are permanent and won't be.

• Klaviyo can log both as bounces, so read the bounce reason, not just the count.

• To improve email deliverability now, check authentication and complaints continuously rather than once.

Gmail used to give senders a warning shot. Shaky mail got deferred or quietly filtered, and you had time to fix things. That's changed. If you run Klaviyo campaigns for an ecommerce store, this is one of the more important sending changes in years.

What changed in November 2025

The rules themselves aren't new. Since February 2024, anyone sending around 5,000 or more emails a day to personal Gmail accounts has needed SPF and DKIM, a DMARC record aligned with the From domain, a spam rate under 0.10% and never reaching 0.30%, and one-click unsubscribe on marketing mail.

At first, enforcement was gentle. A sender with gaps would mostly see temporary errors that told the sending platform to retry. That left breathing room. From November 2025, Google started rejecting more non-compliant traffic outright. That mail doesn't land in spam or sit in a queue. It doesn't arrive.

Temporary vs permanent rejection

Temporary rejection (4xx). Gmail replies with a code such as 421 that means "not now". Maybe a DKIM signature failed once, or volume spiked suddenly. Klaviyo retries, and the email may get through later. Repeated 4xx responses are still a warning sign.

Permanent rejection (5xx). Gmail replies with a code such as 550 5.7.26 for unauthenticated mail. No retry will help. These come from consistent authentication failures, a poor domain reputation or a complaint rate past the line.

The catch for Klaviyo users is that both can end up as bounces. Unless you read the bounce reason, you can't tell a one-off blip from Gmail closing the door on your domain.

Why Klaviyo senders feel this most

Klaviyo brands send big volumes in bursts: launches, sales, BFCM. Volume spikes plus authentication that was set up once and never revisited is exactly the pattern Gmail's enforcement targets.

Many stores still treat deliverability as set-and-forget. That no longer works. Gmail reads recent sending behavior, so one complaint spike or a broken DMARC record can bring rejections within days.

A MailMend on/off A/B test inside Klaviyo. Clearing Gmail's rejection checks gets mail accepted; placement is tested next.

How to improve email deliverability under the new rules

Improving email deliverability now means consistency. Focus here first:

1.  Check authentication monthly, not once. SPF, DKIM and DMARC can break quietly when you add a tool or change DNS. Watch the SPF 10-lookup limit too.

2.  Watch your spam rate in Postmaster Tools. 0.30% is the ceiling. Investigate anything above 0.10%.

3.  Segment by engagement. Cold subscribers drive complaints. Regular suppression is one of the most effective ways of improving email deliverability without changing a word of copy.

4.  Confirm one-click unsubscribe works everywhere. Klaviyo adds compliant headers by default, but custom templates and other tools can break them.

5.  Warm up new sending domains. If you've moved to a new branded domain in Klaviyo, ramp volume gradually.

6.  Read your bounce reasons. Separate 4xx from 5xx, and policy rejections from bad addresses, every week.

Where MailMend fits

Clearing Gmail's checks gets your mail accepted. Email marketing deliverability has a second half though: once Gmail accepts a message, it still decides between Primary and Promotions. MailMend works on that half. It's built for Klaviyo and designed to improve how often your campaigns and flows land in Primary, with no changes to your copy or your list, measured in a native Klaviyo A/B test, MailMend on versus off.

Book a demo to try it. The free trial starts after your first A/B test.

Frequently asked questions

How do I tell a temporary rejection from a permanent one in Klaviyo?

Open the bounce details and read the SMTP response. Codes starting with 4 are temporary. Codes starting with 5 are permanent.

Will Klaviyo retry a temporary rejection?

Yes, deferred messages are retried automatically. Persistent 4xx responses still point at a problem to fix.

What's the fastest way to improve email deliverability?

Fix authentication gaps, suppress disengaged subscribers and keep your Gmail spam rate under 0.10%. Then test where your accepted mail lands.

How is this different from the Promotions tab?

A rejection means Gmail never accepted the email. Promotions is where Gmail files accepted marketing mail. They're separate problems with separate fixes.