"451 ESMTP MailEnable Service temporarily refused connection" error when connecting to SMTP service


The client or server trying to send email to MailEnable receives the error:

451 ESMTP MailEnable Service temporarily refused connection at 10/19/11 00:01:25 from IP (xxx.xxx.xxx.xxx) because the server is too busy.

The SMTP Debug log shows:

ME-E0125: Connection Refused: (xxx.xxx.xxx.xxx) was refused because the inbound connection limit has been reached.


The SMTP service has a setting which allows the administrator to restrict how many concurrent inbound connections can be made to the SMTP service. The message occurs when this limit has been reached.


The server is giving a temporary error to the sender, so servers who receive this message will retry. If you need to increase the number of concurrent connections possible, this can be done through the administration program. The setting can be found in the properties of the SMTP service in the Inbound SMTP tab.  This is accessed by expanding the Servers->localhost->Connectors branch, right clicking on the SMTP icon and selecting Properties from the popup menu. Under the Inbound tab, click Settings and then you can change the maximum number of concurrent connections.

Product:MailEnable (ME-1.X Std-1.X Pro-1.X Ent-1.X)
Class:PRB: Product Problem or Issue
Revised:Wednesday, May 4, 2016