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Mailenable Version: 3.x Problem: Outbound SMTP emails Queued

Occurrence: Random

We are using Mailenable version 3.x on a Windows 2003 Server with 4GB RAM. The server is good on resources and we have plenty of storage space available on our server.

DNS is resolving fine, we have bypassed our firewalls and our mail server have been working fine with the firewall in place too. We have an AV / SPAM filter in front of our email server but that has never disrupted our email service before. No Change has been done on any of our network devices, SPAM Filter or Email Server.

The issue is appearing for the last two days at about the same time, we will get all outbound emails stuck in a queue on our email server, SMTP Logs are fine, if we try to telnet to our email server on port 25 from outside the network, we get the following SMTP ERROR Code :

451 ESMTP MailEnable Service temporarily refused connection at 07/02/11 18:20:41 from     
IP 1.1.1.1) because the server is too busy.

During this time we get delays in receiving emails from external domains. I have checked the Mailenable forums / kb and 451 ESMTP Code causes and resolution, it suggests to increase the inbound connection limit. Our inbound connection limit is set to 32

Thank you !

Resolution : 

MailEnable Knowledgebase Article - Increase Max INBOUND Connections of the SMTP Service

To resolve this issue, increase the Max Inbound Connections of the SMTP service. This setting can be found in the properties of the SMTP service in the Advanced SMTP tab. Or at the following location;

MailEnable Administration Program ->servers ->localhost ->connectors ->SMTP Properties ->Inbound TAB ->Maximum number of concurrent connections.

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2 Answers 2

Any chance your server is under attack? You might check your queue directories to see if they are bogged down with any ongoing heavy loading (possibly from an ongoing attack or error condition).

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hi user48838, thank you for your reply, we have checked the queue directories and it doesn't seem to be under attack - our outbound emails were also stuck around 1000 emails - all legit and from our internal users - any ideas ? –  rihatum Jul 3 '11 at 11:20
1  
It looks like there may be a damaged message in your outbound queue. Is the queue cycling through or just stuck? You might try moving or deleting the oldest messages from the outbound queue. Also time for a chkdsk to ensure there is also no file system issues lurking around which may be leading up to the damage. –  user48838 Jul 3 '11 at 12:22
    
hi user48838, thank you for your input on this, however after googling and increasing the smtp inbound - it seems to resolve the issue. Really grateful for your input on this. Thanks –  rihatum Jul 5 '11 at 4:49
    
Glad that things are working out. –  user48838 Jul 5 '11 at 7:03
up vote 0 down vote accepted
Resolution : 

MailEnable Knowledgebase Article - Increase Max INBOUND Connections of the SMTP Service

To resolve this issue, increase the Max Inbound Connections of the SMTP service. This setting can be found in the properties of the SMTP service in the Advanced SMTP tab. Or at the following location;

MailEnable Administration Program ->servers ->localhost ->connectors ->SMTP Properties ->Inbound TAB ->Maximum number of concurrent connections.
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