The server on Zimbra has been installed and has been working for a long time. There was a problem, when sending letters to one of the domains, the mail does not always pass. I broke through the domain on the site at http://mxtoolbox.com (testing mail servers) and got the result.
smtp mx2.!!!.!!!.ru Reverse DNS does not match SMTP Banner smtp mx2.!!!.!!!.ru Warning - Does not support TLS. smtp mx2.!!!.!!!.ru 15.425 seconds - Not good! on Transaction Time I think that on the server mx2.!!!.!!!.ru set the mode "Tarpitting" (delayed response to receiving a letter).
The question is how to set the duration of the transaction on the Zimbra to solve this problem.
