a have Postgrey service installed (version: 1.3.0 (Build 2018032000)) on my I-MSCP server. I have more than 200 email users under several domains.
So I need this service, but in the days the customers realized that so many email delayed more than 10 hours and in some cases the mails arrive twice.
How can I check that this service working properly?
What config steps do I need to check?