In Wikipedia it sais:
A mail transfer agent (MTA) using greylisting will "temporarily reject" any email from a sender it does not recognize. If the mail is legitimate the originating server will, after a delay, try again and, if sufficient time has elapsed, the email will be accepted.
But how can I find out how long these delays are on my server and on the receiving side?
My goal is to speed up email-traffic with partners using greylisting too and speed up the receiving of the first email someone sends to customers on my server.