Email deliverability

Email deliverability is the rate at which your emails reach the recipient's inbox rather than being rejected, bounced, or filtered to spam.

It's decided by three things, roughly in this order.

Authentication. SPF, DKIM, and DMARC records on the sending domain tell the receiving server that the email is really from you. Google, Yahoo, and Microsoft all require them now for anyone sending volume, and a domain without them starts in the spam folder.

Reputation. Every sending domain and every IP has a history, and the receiving server checks it. New domains have no history, which is why they need warmup. Domains that have been sending to people who delete unread have a bad history, which is why list quality is a deliverability problem and not just a reply-rate problem.

Engagement. Google's filtering in particular watches what recipients do. Opens, replies, and moves-to-inbox help. Deletes, ignores, and spam complaints hurt. A spam complaint rate above 0.3 percent gets a domain throttled at Gmail, and the safe target is under 0.1.

An example

A staffing firm sends 3,000 candidate emails a week from its main domain through its ATS. Candidates ignore most of them and a few mark them as spam. Six months later the firm's business development emails to hiring managers land in junk, even though those emails are well written, because the domain's reputation was built by the candidate blasts. The fix is separate domains for client outreach.

How to measure it

Bounce rate, spam complaint rate, and inbox placement tests against real mailboxes at Google and Microsoft. Open rate is not a deliverability measure; Apple's Mail Privacy Protection has inflated it since 2021 and it no longer tells you anything reliable.

Related terms

Spf dkim dmarc · Email warmup · Sending domain · Spam complaint rate

If you want this run for you, see our cold email agency, or cold email for staffing agencies.