Why "user mail.domain1.ru rejected your message sent to the following email addresses"?

Question

Mail server

Hello.
In the screenshot , 1_a is the client's mail server, s_m is our mail client.
The letter is sent by the client, but it does not reach us, returning the letter with an error to the sender.

Fri 2016-06-10 09:59:02: Session 469568; child 2
Fri 2016-06-10 09:59:02: Accepting SMTP connection from [domain2:26427] to [192.168.3.33:25]
Fri 2016-06-10 09:59:02: --> 220 mail.domain1.ru ESMTP MDaemon 12.5.1; Fri, 10 Jun 2016 09:59:02 +0300
Fri 2016-06-10 09:59:02: <-- EHLO domain2.ru
Fri 2016-06-10 09:59:02: EHLO/HELO response delayed 2 seconds
Fri 2016-06-10 09:59:04: --> 250-mail.domain1.ru Hello domain2.ru, pleased to meet you
Fri 2016-06-10 09:59:04: --> 250-ETRN
Fri 2016-06-10 09:59:04: --> 250-AUTH LOGIN CRAM-MD5 PLAIN
Fri 2016-06-10 09:59:04: --> 250-8BITMIME
Fri 2016-06-10 09:59:04: --> 250 SIZE
Fri 2016-06-10 09:59:04: <-- MAIL FROM:<[email protected]> SIZE=63184
Fri 2016-06-10 09:59:04: --> 550 mail.domain1.ru does not accept mail from domain2.ru
Fri 2016-06-10 09:59:04: SMTP session terminated (Bytes in/out: 62/255)

domain2 is the sender's domain, domain1 is ours, the receiving domain.

Answer 1

Looks like this - www.exchangerus.ru/2008/06/17/550-we-do-not-accept... or www.linux.org.ru/forum/admin/10449744
Left x-originating-ip (dynamic , unconfigured).

Answer 2

Judging by the text of error 550, your domain 1......a.ru is blacklisted by the recipient. The reason for blacklisting can only be explained by the administrator of the recipient's server.
PS Sorry for the obviousness, but the problem in this case is who needs the letter to reach. If only you - then your problem. If the recipient - then the problem is the recipient.