Email sending error because of too many connections

There were many reason of email sending error. One of them is because of too many connections to the server. This is the sample MDaemon email server logs of sending mail failure because of too many connections to the mail server.

Sender user is: user@mycompany.com
Recipient user is: theuser@telkom.net

In this log there is line:

Fri 2010-03-12 07:41:33: <-- 421 #4.4.5 Too many connections to this host Fri 2010-03-12 07:41:33: --> QUIT
Fri 2010-03-12 07:41:33: Socket connection closed by the other side (how rude!)

This mean the recipient mail server could not receive email from user@mycompany.com because in the same time the server receipt too many connection (may be from other email server) that could not be handled.

MDaemon server (Sender user mail server) will automatically resend the mail from user@mycompany.com to theuser@telkom.net next time depend on the setting of MDaemon mail server.

Fri 2010-03-12 07:41:33: Session 8894; child 10
Fri 2010-03-12 07:41:31: Parsing Message
Fri 2010-03-12 07:41:31: From: user@mycompany.com
Fri 2010-03-12 07:41:31: To: theuser@telkom.net
Fri 2010-03-12 07:41:31: Subject: Kelebihan Pengobatan
Fri 2010-03-12 07:41:31: Message-ID:
Fri 2010-03-12 07:41:31: MX-record resolution of [telkom.net] in progress (DNS Server: 202.152.0.2)...
Fri 2010-03-12 07:41:31: * P=011 S=000 D=telkom.net TTL=(0) MX=[mx2.mail.plasa.com] {222.124.18.72}
Fri 2010-03-12 07:41:31: * P=011 S=001 D=telkom.net TTL=(0) MX=[mx1.mail.plasa.com] {222.124.18.71}
Fri 2010-03-12 07:41:31: Attempting MX: P=011 S=000 D=telkom.net TTL=(0) MX=[mx2.mail.plasa.com] {222.124.18.72}
Fri 2010-03-12 07:41:31: Attempting SMTP connection to [222.124.18.72 : 25]
Fri 2010-03-12 07:41:31: Waiting for connection...
Fri 2010-03-12 07:41:32: Connection established (192.168.0.25 : 2790 -> 222.124.18.72 : 25)
Fri 2010-03-12 07:41:32: Waiting for protocol initiation...
Fri 2010-03-12 07:41:32: <-- 421 #4.4.5 Too many connections to this host. Fri 2010-03-12 07:41:32: --> QUIT
Fri 2010-03-12 07:41:32: Attempting MX: P=011 S=001 D=telkom.net TTL=(0) MX=[mx1.mail.plasa.com] {222.124.18.71}
Fri 2010-03-12 07:41:32: Attempting SMTP connection to [222.124.18.71 : 25]
Fri 2010-03-12 07:41:32: Waiting for connection...
Fri 2010-03-12 07:41:32: Connection established (192.168.0.25 : 2798 -> 222.124.18.71 : 25)
Fri 2010-03-12 07:41:32: Waiting for protocol initiation...
Fri 2010-03-12 07:41:33: <-- 421 #4.4.5 Too many connections to this host. Fri 2010-03-12 07:41:33: --> QUIT
Fri 2010-03-12 07:41:33: Socket connection closed by the other side (how rude!)
Fri 2010-03-12 07:41:33: This message is 1 days old; it has 4 days left to get delivered
Fri 2010-03-12 07:41:33: SMTP session terminated (Bytes in/out: 94/12)