The situation is as follows. 1:1 like here: [exim] Exim stucks after bdat command when sending to google
And it is interesting that the problem is observed only with sending emails to gmail.
For some reason, a rather large queue of emails has formed on the HestiaCP server. We started investigating and it turned out that after we added a rule to the firewall that says allow everything, on all ports. After that, the mail went without any problems. The question is, maybe you had a similar situation. As you can see in the Internet there is information about a similar problem. Do you have any information on what ports need to be opened additionally so that mail is sent to the gmail servers without any problems?