Mailenable Version: 3.x Problem: Outbound SMTP emails Queued
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 18.104.22.168) 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 !
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.