Mail does not come to exchange 2016?

Question

Microsoft Exchange

Good afternoon, letters do not come in exchenge 2016, I send a letter via mail, after some time, a letter arrives with an error:
This letter was created automatically by the Mail.Ru server, you do not need to respond to it.

Unfortunately, your message could not be delivered to one or more recipients:

*@*
retry timeout exceeded

We recommend that you check the correctness of the recipient addresses.

**********************

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

*@*
retry timeout exceeded

------ This is a copy of the message, including all the headers. ------

Return-path: <*@mail.ru>
Received: from [10.161.19.14] (port=33592 helo=f481.i.mail.ru)
by fallback14.m.smailru.net with esmtp ( envelope-from <*@mail.ru>)
id 1jZXq2-0001Jc-AN
for [email protected]; Fri, 15 May 2020 13:45:10 +0300
DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=mail.ru; s=mail2;
h=Content-Type:Message-ID:Reply-To:Date:MIME-Version:Subject:To:From; bh=IOrnrVn6M950PfArE+DI9zixsjsRjeMl0Xc6GSiYqwE=;
b = B99fwojcRiYw9d + j + fldZli / 26sqHFB3uOFYl36Dtb87 + V5HGmYX22sUcgzlmO5IIwebdAMEaAndWZtOTsONY4HUeMFEbkQYbBsG + A2dXhbquP5GYWk25Ruu3gFsmN0P3UdpnqwnczrOl16JgC + Wa5Lnzy4r7Kthe21mtCK5ITs =;
Received: by f481.i.mail.ru with local (envelope-from <*@mail.ru>)
id 1jZXpr-0005NE-VQ
for [email protected]; Fri, 15 May 2020 13:45:00 +0300
Received: by e.mail.ru with HTTP;
Fri, 15 May 2020 13:44:59 +0300
From: =?UTF-8?B?0J7QntCeICDQk9CY0J8gLdCt0LvQtdC60YLRgNC+ICDQsy7Qo9GE0LA=?= <*@mail.ru>
To: =?UTF-8?B?c3VwcG9ydA==?= <*@*>
Subject: =?UTF-8?B?0KHRh9C10YI=?=
MIME-Version: 1.0
X-Mailer: Mail.Ru Mailer 1.0
Date: Fri, 15 May 2020 13:44:59 +0300
Reply-To :=?UTF-8?B?0J7QntCeICDQk9CY0J8gLdCt0LvQtdC60YLRgNC+ICDQsy7Qo9GE0LA=?=
X-Priority: 3 (Normal)
Message-ID: <[email protected]>
Content-Type: multipart/alternative;
boundary="--ALT--bDf527345339E89e97c0aB89fCe192971589539499"

Answer 1

The error itself indicates that your server (more precisely, the mail.ru server), according to RFC, tried to hammer for several days, but could not access the server, and the user received NDR "retry timeout exceeded".
Judging by the direction of the letter from mail.ru to your server [email protected]*******o.ru
It turns out that the firewall closed port 25 to your server.
Although I successfully connected to mail.g*****o.ru...
Need more details.