What Is Email Deliverability? What to Check First

Email deliverability is the share of the emails you send that actually land in the recipient's primary inbox, not in spam or the promotions tab. It is not the same thing as "sent" or "delivered". An email can count as delivered and still never be seen by anyone.

Delivered is not the same as landed

There are two steps. First the recipient's mail server accepts the message, which is delivery. Then Gmail or Outlook decides where it goes, which is deliverability. The first step shows up in your sending tool's report. The second does not show up there at all.

So you can have a 0% bounce rate, 100% delivered, and every message sitting in spam. That is how a campaign looks healthy on the dashboard and still produces zero replies.

What decides it

Mailbox providers decide on trust. Six things build it or burn it:

1. Domain and mailbox reputation. The sending history of the domain. A brand-new domain with no history is not treated as suspicious, but it is not trusted either. My standing practice is new domains and about four weeks of warm-up before any real send.
2. Authentication. SPF, DKIM and DMARC are three DNS records that prove the email really came from the domain it claims. Without all three, messages get filtered without anyone asking.
3. Spam complaints. Every "report spam" click hurts. Google's target is under 0.1% complaints, and you should never reach 0.3%. Its guidelines are written for high-volume senders, and I apply them at small volume too, since there is no reason to wait for the official threshold. On my side, a warning from 0.1%, and above 0.3% volume stops.
4. Bounces. Emails that come back because the address does not exist. Under 2% is fine, 2% to 5% is a warning, above 5% means stop sending and check the list.
5. Volume and pacing. Up to 15 emails a day per mailbox, spread across several mailboxes and several domains. One mailbox pushing out hundreds a day looks like a spammer, and gets treated like one.
6. Content and list. Links and attachments in a first cold email lower placement, and so do spam words and heavy formatting. Instead of a link, write "want me to send it?". An old list produces bounces and complaints.

How to tell there is a problem

Open rate is not a reliable placement metric (some opens are automated, and some tools do not track them at all). My metric is replies. Three signs:

1. A sudden drop in replies with no change to the message.
2. Bounces climbing above 2%.
3. One mailbox degrading while the others stay healthy (check warm-up score and blacklist status).

When that happens the order is fixed: infrastructure before copy. I wrote the four checks in Deliverability before copy, and the mailbox, domain and provider diagnosis order in what to replace first.

Common questions

What is the difference between delivery and deliverability?

Delivery: the recipient's server accepted the message. Deliverability: where it lands, primary inbox, promotions or spam.

What is good deliverability?

There is no agreed magic number, and I am wary of anyone who promises one. The thresholds I work with: bounces under 2%, complaints under 0.1%, and reply rates that stay stable over time.

How long do you warm up a new domain?

About four weeks before any real sending. That is my practice.

Can you fix a burned domain?

Sometimes, once it is off the blacklist and you rebuild its reputation. Usually the volume moves to a new domain. That is why a company's main domain never sends cold email.

What it looks like in practice

An international freight client: 12 mailboxes across 4 dedicated domains, and the client's own domain never used for sending. The result: 213 leads, 15+ meetings and 8+ new clients within 4 months (full case). Deliverability was the precondition, not the story.

It is not impressive and it does not show up in any chart. It decides whether everything else gets read. The whole process, from list to meeting, is in B2B lead generation.