What is the difference between valid and deliverable?

Verification answers a question about the recipient. Deliverability answers a question about you, and no check of their mailbox can settle it.

Picture a Gmail address belonging to a real person who reads it daily. Perfectly valid. Now send from a domain with no DKIM signature, on an IP that Spamhaus listed last week, to someone who never asked. Nothing arrives, and the address was never the problem.

Some vendors use deliverable as their label for a valid verdict, which blurs a distinction worth keeping. It suggests a promise about arrival that no verifier is in a position to make.

The spam folder sits inside this gap and complicates it further. A message can be accepted by the server, counted as delivered in every report you can see, and filed where nobody looks. Delivery rate counts it as a success.

So both halves of the work are needed and neither substitutes for the other. Verification removes the addresses that cannot receive anything. Reputation, authentication and engagement decide whether the ones that remain see your message.

Say two companies mail the same 10,000 verified addresses on the same day. Every address is valid. Sender A has used the same authenticated domain for three years and writes to people who open its mail. Its report shows 9,960 accepted, and nearly all of those reach the inbox.

Sender B registered its domain last month and hasn't set up DKIM. It's mailing these people for the first time. Its report might show 3,000 messages deferred with temporary errors, and most of the rest accepted but filed as spam. A few hundred people see the message.

These figures are made up, but the pattern is real, and the list played no part in it. Both senders had perfect data. Whatever separated them happened after the server agreed that the mailbox exists, and a verifier stops looking at exactly that point.

Delivery rate is the share of sent messages that a receiving server accepted. It's the number in your campaign report, and it counts a message in the spam folder as a success.

Inbox placement is the share of accepted messages that reached the inbox. No mailbox provider reports it to you, so your own sends can't measure it directly. Tools estimate it by mailing a panel of test addresses and looking at where each copy landed. Useful, but it's an estimate from a sample.

Open rate used to stand in for placement, and it's less reliable than it was. Apple's mail privacy feature, launched in 2021, loads images in the background for every message, whether or not the person ever reads it. A large share of your opens may now be machines.

Put together, a 99% delivery rate tells you the list is clean. It can't tell you whether anyone saw the mail. Clicks and replies are the signals that still mean a person was there.