Email Deliverability
By Federico Donatone · Updated October 15, 2026Email deliverability is the share of your sent emails that reach the recipient's inbox instead of bouncing or landing in spam. It depends on four things: authenticated sending domains, a verified contact list, a steady daily volume per mailbox, and messages relevant enough that recipients do not report them as spam.
Email deliverability vs email delivery
Delivery and deliverability sound alike but measure different things. An email is delivered when the receiving server accepts it. It is deliverable, in the sense that matters, when it reaches the primary inbox where a person will actually see it. A message filtered to spam still counts as delivered, which is why a campaign dashboard can show almost everything delivered and still produce no replies.
For B2B teams, that gap decides whether outbound works. An email that lands in spam costs the same to send as one that lands in the inbox, and it quietly drags down the reputation of the domain that sent it.
What decides email deliverability
Three parties decide where a message lands: the receiving mail system (usually Google or Microsoft in B2B), the recipient, whose replies and spam reports train the filter, and you, the sender. You control the sender side completely. Check it in this order and stop at the first layer that fails:
| Layer | What it means | What to check |
|---|---|---|
| Infrastructure | Separate sending domains that prove who sent the email | SPF, DKIM and DMARC pass and align |
| List | Every address exists and fits your target | Outside verification, no guessed emails |
| Volume | A steady sending pattern per mailbox | Daily sends per mailbox, slow ramp |
| Relevance | Recipients want the message | Spam reports, replies, opt-outs |
Many teams start by rewriting copy because it is the easiest thing to change. A better email on a broken setup still lands in spam, so work down the table from the top and fix each layer before moving to the next.
What Gmail and Yahoo require from senders
Since February 2024, Google and Yahoo have enforced rules for bulk senders. Senders of 5,000 or more messages a day to Gmail must authenticate with SPF, DKIM and DMARC, offer one-click unsubscribe, and keep the spam complaint rate under 0.3% (Google's email sender guidelines).
These rules target personal inboxes, and most B2B cold email goes to company mailboxes on Google Workspace or Microsoft 365. Treat them as the minimum bar anyway. Business filters check the same authentication and react to the same complaints.
How to improve email deliverability
- Send cold email from dedicated sending domains, never from the domain your company runs on.
- Publish SPF, DKIM and DMARC on every sending domain before the first email goes out.
- Verify every address with an outside verifier and drop catch-all and guessed emails.
- Ramp new mailboxes slowly and cap each one at a fixed daily number.
- Write emails specific enough that they would not work if you swapped in another prospect's name.
- Watch bounces, replies and spam complaints by mailbox, and pause any mailbox where they jump.
Our cold email deliverability checklist covers each step in detail. For a quick self-check, our free cold email domain checker scores a domain on MX, SPF, DKIM, DMARC and blocklist status. When the problem survives the checklist, an email deliverability consultant can read message headers, bounce codes and provider data to find the cause.