The problem it solves
You write a good email, send it to five hundred customers, and a large share never see it — not because they ignored it, but because it went to spam or was never delivered at all.
No amount of better subject lines fixes that. Deliverability is upstream of everything else in email.
The technical half
Three records on your domain tell mail providers that email claiming to come from you actually does:
- SPF — which servers are allowed to send as your domain
- DKIM — a signature proving the message was not altered
- DMARC — what a provider should do when a message fails the first two
This is a one-time setup and it is not optional any more. Major mailbox providers have tightened requirements for bulk senders, and mail from domains without proper authentication is treated with suspicion by default.
If you have never had these set up, that is almost certainly your problem.
The list half
Remove hard bounces immediately. An address that no longer exists, mailed repeatedly, tells providers you are not paying attention.
Remove the long-dormant. Someone who has not opened anything in a year or more is not a subscriber, they are a liability. Mailing them lowers your engagement rate, which lowers your inbox placement for everyone else.
Never buy addresses. Purchased lists contain spam traps — addresses that exist specifically to catch senders who bought a list — and hitting one can damage your reputation for a long time.
Watch complaints. People marking you as spam is the most damaging signal there is, and it usually comes from mailing too often or from a hidden unsubscribe.
Why shrinking the list helps
Owners resist deleting contacts, because the number feels like an asset. But providers judge you on engagement, not size.
A list of two hundred people who open is worth far more than two thousand where four hundred do — the small list reaches the inbox and the large one does not.
What good looks like
Authentication in place, bounces removed automatically, dormant contacts pruned on a schedule, complaints monitored, and a visible unsubscribe in every send.
None of it is glamorous. All of it decides whether the rest of your email budget does anything.
Checking your position
Send yourself a test to a couple of different mail providers and see where it lands. If it is not in the main inbox, start here before writing another campaign.
Frequently asked questions
What are SPF, DKIM and DMARC?
Records on your domain that let mail providers verify email claiming to be from you really is. It is a one-time setup, and major providers now treat unauthenticated bulk mail with suspicion by default.
Should I delete inactive subscribers?
Yes. Providers judge you on engagement, not list size. Someone who has not opened anything in a year lowers your inbox placement for everyone else on the list.
Why is a smaller list sometimes better?
Two hundred people who open reach the inbox. Two thousand where most ignore you do not — the engagement signal decides placement, and it is a rate, not a count.
How do I tell if I have a deliverability problem?
Send a test to a couple of different mail providers and see where it lands. If it is not in the main inbox, fix that before writing another campaign.