Email Campaign Deliverability

Deliverability is decided before you send

Most advice about the spam folder is about wording, which is the least important part. Mailbox providers weigh authentication, complaint rate, whether recipients engage, and whether people who want out can actually get out. A campaign that fails on those does not get rescued by a better subject line.

The mechanical checks are the ones worth being strict about, because they are binary and you can verify them. Is the sending domain authenticated. Does the unsubscribe link work. Is the list people who asked to hear from you.

Verify the unsubscribe link actually resolves

This is the failure worth checking first, because it is silent. A footer link and a List-Unsubscribe header can both point at a URL that was never implemented, and on many platforms an unrouted path still answers with a 200 and a generic page rather than an error. The send succeeds, the campaign looks fine, and nobody can opt out.

The tell is your opt-out rate. If a list of thousands has produced almost no unsubscribes across several campaigns, that is not unusually loyal readers. Something is broken. Click the link from a real delivered email and confirm the flag is set on the account.

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Frequently Asked Questions

What affects email deliverability most?

Authentication, complaint rate, recipient engagement, and a working unsubscribe. Subject-line wording matters far less than most advice suggests.

How do I know if my unsubscribe link is broken?

Check your opt-out rate. Near-zero unsubscribes across several campaigns usually means the link is not working. Click one from a real delivered email and confirm it records the opt-out.