Glossary
Deliverability
Also called inbox placement.
Last reviewed 18 September 2026
What is email deliverability?
Deliverability is the share of the mail you send that reaches the inbox of the person you addressed it to, as distinct from delivery, which is only the share the receiving server accepted rather than bounced.
A message can be delivered and never seen: accepted at the door, filed straight into the spam folder, counted as a success by the sending side and read by nobody. The receiving provider does not report which folder it chose and will not, which is why deliverability is inferred from complaint rates, bounces and behaviour rather than read off a dashboard.
For a small sender it comes down to authenticated mail on a domain you control, a spam complaint rate under the level the large providers enforce, hard bounces suppressed on the first failure, and a list that confirmed it wanted the mail.
See also
- Delivery rate
A delivery rate is the share of a send that the receiving mail server accepted instead of bouncing, and it says nothing at all about whether any of it reached an inbox.
- Sender reputation
Sender reputation is what a mailbox provider has learned about the domain and the infrastructure your mail comes from, assembled from complaints, bounces, spam trap hits and how the people who receive your mail behave, and it is what decides the folder.
- Spam complaint rate
A spam complaint rate is the count of people who pressed the spam or junk button divided by the mail delivered to that provider over a window it chooses, and Google and Yahoo both name 0.3 per cent as the level to stay under and 0.1 per cent as the level to aim at.
- Bulk sender requirements
The bulk sender requirements are the list Google and Yahoo both began enforcing in February 2024: SPF and DKIM on the sending domain, a DMARC record on the From domain, one-click unsubscribe in the headers, unsubscribe requests honoured within two days, and a spam complaint rate under 0.3 per cent.
- Seed list
A seed list is a set of addresses you control at several mailbox providers, mailed alongside a real send so that you can open each account yourself and see which folder the message landed in.
Read next
This term is covered properly in Email deliverability for small senders: authentication and reputation, which is a longer piece on the subject.
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