Email deliverability
Deliverability is whether your mail reaches the inbox rather than the spam folder or nowhere at all. It is not one setting. It is the combined result of authentication, the reputation of your domain and sending address, how people react to your mail, and how clean your list is. Every part of it is earned over time and can be lost in a single campaign.
At a glance
- Category
- Deliverability
- Not the same as
- Delivery — acceptance by the server is not placement
- Built from
- Authentication, reputation, engagement, list quality
- Judged per
- Mailbox provider, and mostly by sending domain
- Measured by
- Complaint rate, bounce rate, clicks and replies
How it works
Every receiving organisation runs its own filter and keeps its own view of you. On arrival it checks authentication, looks up what it knows about your sending domain and address, weighs the content, and consults how its own users have treated your mail before. The outcome is a placement decision nobody reports back to you. Because the inputs are cumulative, the same message can land in the inbox at one provider and in junk at another on the same afternoon.
Why it matters
Deliverability is the difference between mail that was sent and mail that was read, and nothing else in your sending stack matters if it is bad. It is also the one part you cannot buy: no provider, address or plan makes a list of unconsented addresses deliverable. Treating it as a property you maintain — authenticate everything, mail people who asked, remove people who bounce or complain — is the only approach that survives a change of provider.
Example
A team notices replies falling while the delivered count stays flat. Authentication is checked first and is fine. The complaint rate at one provider turns out to have tripled after a campaign to addresses last mailed two years ago. They stop mailing the dormant segment, keep sending to the engaged one, and watch the rate fall back over several weeks. Nothing about the content or the provider changed.
Common mistakes
- 01Reading delivered as inbox, which hides a filtering problem behind a number that looks like success.
- 02Changing sending provider to fix a reputation problem, which moves the same list to a new address and repeats the outcome.
- 03Mailing an old list to reactivate it, which is the single fastest way to raise complaints and hit spam traps at once.
- 04Judging a whole account by one aggregate number, when placement is decided separately by every mailbox provider your readers use.
Related terms
Frequently asked questions
Can I measure inbox placement directly?
Not from your own data, because folder placement is never reported back. Seed accounts and provider postmaster tools give partial views, and clicks and replies are the most honest proxy most teams have.
Does buying a dedicated IP improve deliverability?
Only for senders with enough steady volume to build a reputation on it. For everyone else it isolates a sender who has too little traffic to be judged, which usually makes placement worse.
How long does it take to recover from a bad patch?
Usually weeks rather than days, because reputation is a rolling view. Sending less, to people who engage, is what shortens it; sending more to prove you are legitimate lengthens it.
Sources
Last updated 16 September 2026.
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