Email deliverability in 2026: why your campaigns stopped landing

Your open rate has been falling for six months. The team keeps rewriting subject lines. Nothing changes.

That is because the problem is almost never the subject line. It is that a growing share of your emails never reach the inbox at all, and every campaign sent to an unengaged list makes the next one land worse.

Deliverability is the least glamorous part of email marketing and the one that decides whether the rest matters.

Diagnose before you fix

Open a report and split open rate by recipient domain. Gmail, Outlook, corporate domains, everything else.

If the numbers are broadly similar, you have a content problem and rewriting is the right move. If Gmail is at 12 percent while Outlook sits at 34 percent for the same send, you have a placement problem at one provider, and no subject line will fix it.

This five-minute check tells you which of the next two sections applies. Most teams skip it and spend a quarter optimising the wrong thing.

The three layers of deliverability

Layer one: authentication. SPF, DKIM and DMARC are no longer optional, and the bar rose again for bulk senders. Publish all three. Set your DMARC policy to something other than none, because a policy of none tells mailbox providers you are not serious about protecting your own domain. This is a one-off configuration task that most teams did partially and never revisited.

Layer two: reputation. Mailbox providers score your sending domain and IP on how recipients behave. Opens and replies help. Deletions without opening, spam complaints and hard bounces hurt. Reputation is earned slowly and lost fast, and it belongs to the domain, so a burned reputation follows you to a new email platform.

Layer three: engagement. This is where most B2B senders fail. Sending to everyone every time feels efficient. It is the fastest way to teach a provider that your mail is ignorable, because the unengaged majority drags down the signal from the engaged minority.

The list hygiene most teams refuse to do

Here is the conversation we have with almost every client, and it is uncomfortable because it involves deleting contacts someone paid for.

Segment the list by last engagement. Anyone who has not opened or clicked in 90 days goes into a suppression segment. Not deleted immediately, suppressed from regular sends.

Run one re-engagement sequence to that segment. Two emails, direct, asking whether they still want to hear from you. Whoever engages comes back to the main list. Whoever does not gets removed.

The objection is always the same: the list will shrink. Yes. It will shrink to the people who were ever going to buy anything, and your delivery to them improves because the provider stops seeing a mass of ignored mail from your domain.

We have run this on lists that lost 40 percent of their contacts and gained more actual replies the following month. The vanity metric went down. The pipeline went up.

A large list that ignores you is not an asset. It is a reputation liability you pay to store. MyDigipal

Rebuilding a burned reputation

Suppose the damage is already done. Sending volume stays flat and placement keeps degrading. You cannot fix this by sending better emails to the same list, and you cannot fix it quickly.

The process is a warm-up, and it is deliberately slow.

Start with your most engaged segment only. People who opened or clicked in the last thirty days. Send to them and nobody else for two weeks. The point is to give mailbox providers a run of messages that get opened, so the signal attached to your domain improves.

Then widen in steps. Add the sixty-day segment, hold for a week, watch placement by provider. Add ninety days, hold again. If a step degrades your numbers, go back one and stay there longer.

Expect four to six weeks before the picture changes materially. Teams give up in week two, resume sending to everyone, and undo the work.

Two things that accelerate it. Replies are the strongest positive signal available, so a campaign that asks a genuine question and gets answers is worth more than one that gets clicks. And removing hard bounces immediately matters more during a rebuild than at any other time.

The metrics you can no longer trust

Worth stating plainly, because plenty of teams still report on numbers that stopped meaning anything.

Open rates became unreliable once mailbox providers started pre-fetching images on behalf of users. An open can now mean a machine loaded a pixel. Directionally the metric still tells you something, particularly when you split it by provider as described above, but it is not a measure of human attention any more.

What to report instead: replies, clicks through to a tracked destination, and pipeline attributed to the campaign. All three are harder to collect and all three survive contact with a CFO.

This is why the deliverability fix and the measurement fix are the same project in practice. If your email platform is the only system that knows what happened, you cannot prove the channel works, and you cannot diagnose it when it stops working.

The GDPR angle you should not ignore

Transparency is the European enforcement priority for 2026, and list hygiene sits directly on top of it. If you cannot say where a contact came from, when they consented and how long you intend to keep them, that contact is a compliance risk as well as a deliverability drag.

The two problems have the same fix. A clean list with documented consent and stated retention periods performs better and audits better. We wrote about the transparency requirements in detail, and the practical overlap is close to total.

What to do this week

1. Split open rates by recipient domain. Decide whether this is placement or content.
2. Check SPF, DKIM and DMARC are all published, and move DMARC off a policy of none.
3. Build the 90-day engagement segment. Look at how large it is. Sit with that number.
4. Run one re-engagement sequence, then suppress the non-responders.
5. Fix the tracking so you measure replies and pipeline, not opens, since open rates became unreliable when providers started pre-fetching images. That measurement work is the same foundation everything else rests on.

Deliverability is not a campaign you run once. It is a discipline you keep, and the teams that keep it end up with smaller lists that produce more revenue than their competitors’ large ones.

If you want to know what a full deliverability audit and rebuild would cost on your setup, the calculator gives you a range.

Sources: RGPD 2026, new obligations and database management for SMEs - GDPR compliance guide for businesses, 2026