Why can't Mdaemon send outgoing mail?

Question

Mail server

Hello!
The mail server is Mdaemon 15.0.1. Operating system - Windows Server 2003 R2 Enterprise Edition.
Some messages are not sent and remain in the Remote queue. The following messages are in the SMTP out log:
1.
Tue 2018-12-11 11:07:45.831: Session 517348; child 0001
Tue 2018-12-11 11:07:45.831: Parsing message
Tue 2018-12-11 11:07:45.831: * From: [email protected]
Tue 2018-12-11 11:07:45.831: * To: [email protected]
Tue 2018-12-11 11:07:45.831: * Subject:
Tue 2018-12-11 11:07:45.831: * Size (bytes): 847427
Tue 2018-12-11 11: 07:45.831: * Message-ID: <[email protected]>
Tue 2018-12-11 11:07:45.847: Resolving MX record for mrser.ru (DNS Server: 192.168.5.129)...
Tue 2018-12-11 11:07:46.003: * P=020 S=000 D =mrser.ru TTL=(10) MX=[mail.mrser.ru]
Tue 2018-12-11 11:07:46.003: * P=030 S=001 D=mrser.ru TTL=(10) MX=[ mail1.mrser.ru]
Tue 2018-12-11 11:07:46.003: Attempting SMTP connection to mail.mrser.ru
Tue 2018-12-11 11:07:46.003: Resolving A record for mail.mrser.ru (DNS Server
: 192.168.5.129)
... :46.003: Attempting SMTP connection to 92.42.8.82:25
Tue 2018-12-11 11:07:46.003: * 92.42.8.82 in connection failure cache for up to 5 minutes due to previous connection failure(s)
Tue 2018-12-11 11:07:46.003: Attempting SMTP connection to mail1.mrser.ru
Tue 2018-12-11 11:07:46.003: Resolving A record for mail1.mrser.ru (DNS Server: 192.168.5.129) ...
Tue 2018-12-11 11:07:46.003: * D=mail1.mrser.ru TTL=(8) A=[91.143.157.2]
Tue 2018-12-11 11:07:46.003: Attempting SMTP connection to 91.143.157.2:25
Tue 2018-12-11 11:07:46.003: Waiting for socket connection...
Tue 2018-12-11 11:07:46.034: * Connection established 192.168.5.133:2913 --> 91.143. 157.2:25
Tue 2018-12-11 11:07:46.034: Waiting for protocol to start...
Tue 2018-12-11 11:07:46.050: <-- 220 mail.mrser.ru ESMTP MDaemon 15.0.3; Tue, 11 Dec 2018 11:07:45 +0300
Tue 2018-12-11 11:07:46.066: --> EHLO mail2.dgstk.ru
Tue 2018-12-11 11:07:46.081: <-- 250-mail.mrser.ru Hello mail2.dgstk.ru, pleased to meet you
Tue 2018-12-11 11:07:46.081: <-- 250- ETRN
Tue 2018-12-11 11:07:46.081: <-- 250-AUTH LOGIN CRAM-MD5 PLAIN
Tue 2018-12-11 11:07:46.081: <-- 250-8BITMIME
Tue 2018-12-11 11: 07:46.081: <-- 250-ENHANCEDSTATUSCODES
Tue 2018-12-11 11:07:46.081: <-- 250 SIZE 16000000
Tue 2018-12-11 11:07:46.081: --> MAIL From: SIZE=847427
Tue 2018-12-11 11:07:46.112: <--250 2.1.0 Sender OK
Tue 2018-12-11 11:07:46.112: --> RCPT To:
Tue 2018-12-11 11:07:46.144: <-- 250 2.1.5 Recipient OK
Tue 2018-12-11 11:07:46.144: --> DATA
Tue 2018-12-11 11:07:46.159: <-- 354 Enter mail, end with .
Tue 2018-12-11 11:07:46.159: Sending to [91.143.157.2]
Tue 2018-12-11 11:08:05.175: * Socket error 10054 - The connection was restarted on the other end!
Tue 2018-12-11 11:08:05.175: Error writing to socket
Tue 2018-12-11 11:08:05.175: Socket connection closed by the other side (how rude!)
Tue 2018-12-11 11:08 :05.175: * Socket error 10053 - Connection aborted.
Tue 2018-12-11 11:08:05.175: Connection
terminated Tue 2018-12-11 11:08:05.175: * This post is 2 minutes old; 58 minutes left in this queue
2.
Tue 2018-12-11 11:07:55.941: Session 517355; child 0003
Tue 2018-12-11 11:07:55.941: Parsing message
Tue 2018-12-11 11:07:55.941: * From: [email protected]
Tue 2018-12-11 11:07:55.941: * To: [email protected]
Tue 2018-12-11 11:07:55.941: * Subject:
Tue 2018-12-11 11:07:55.941: * Size ( bytes): 1609218
Tue 2018-12-11 11:07:55.941: * Message-ID:
Tue 2018-12-11 11:07:55.956: Resolving MX record for mail.ru (DNS Server: 192.168.5.129).. Tue 2018-12-11
11:07:55.956: * P=010 S=000 D=mail.ru TTL=(9) MX=[mxs.mail.ru]
Tue 2018-12-11 11:07:55.956 : Attempting SMTP connection to mxs.mail.ru
Tue 2018-12-11 11:07:55.956: Resolving A record for mxs.mail.ru (DNS Server: 192.168.5.129)...
Tue 2018-12-11 11: 07:55.956: * D=mxs.mail.ru TTL=(0) A=[94.100.180.104]
Tue 2018-12-11 11:07:55.956: * D=mxs.mail.ru TTL=(0) A =[94.100.180.31]
Tue 2018-12-11 11:07:
55.956 : Randomly picked 94.100.180.31 from list of possible hosts
:07:55.956: Waiting for socket connection...
Tue 2018-12-11 11:08:16.941: * Socket error 10060 - Connection timed out.
Tue 2018-12-11 11:08:16.941: * 94.100.180.31 added to connection failure cache for 5 minutes
Tue 2018-12-11 11:08:16.941: * This message is 0 minutes old; 60 minutes left in this queue Tue 2018-12-11
11:08:16.941: SMTP session terminated (Bytes in/out: 0/0)

Answer 1

Sometimes you just need to wait until the letters go online.