← Glossary
Delivery
What is Greylisting?
Deliberately rejecting the first delivery attempt from an unknown sender and accepting the retry.
How it works in practice
Legitimate servers retry after a few minutes; many spam tools don't. For you it appears as a temporary 4xx and the message arrives later, with no action needed.
The common mistake
Treating a greylisting deferral as a block and changing infrastructure.
Check it yourself
Related terms
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