- Plesk for Linux
- Delivery of notification mails from Amazon SES delayed for several hours.
The following error can be found in
PLESK_INFO: milter-reject: DATA from a10-20.smtp-out.amazonses.com[18.104.22.168]: 451 4.7.1 Service unavailable - try again later;
- Grey-listing is enabled on the server.
Mail is being deferred by grey-listing service.