This guide will show you how to disable greylisting for your domain in Plesk.
Greylisting protects your domain from spam by declining the first connection attempt from the sending server, and then accepting a later connection.
This can cause delays in email receipt and in some cases (where sending servers use multiple different servers for sending email) can cause messages to not be received.
Steps to disable greylisting
1) Log in to Plesk
2) Choose the “Mail Settings” button under the domain you wish to adjust
3) Uncheck the box beside “Switch on greylisting spam protection for all mail accounts under this domain” and click OK