I am using MailEnable Enterprise Edition 6.53.

On one of my PostOffices I have a group address set up with 5 members in the group. Under normal circumstances when someone sends a mail to this group then the mail gets successfully forwarded to all 5 members in the group. However, every now and then when a recipient sends to the group they get a bounce back message from us that the mail could not be delivered because one of the user's addresses was not found on the server. This could happen for any one of the 5 users in the group.

The error message looks like:

Message could not be delivered. Error was: The email address is not available on this system

The following recipient(s) could not be reached:

[SF:mydomain.com/my_username]

What could be causing this and how do I fix it? Obviously the mailbox DOES exist as, under normal circumstances, when someone mails the group the mail gets delivered successfully and forwarded to all group members. All the mailboxes most definitely DO exist on the system.

EDIT:

I have done more investigation and I see an error in Windows Event Viewer:

MailEnable Database Provider error: 0
FAILURE: (SQLDriverConnect), Module: MEIMAPS.exe; Error: [Microsoft][ODBC SQL Server Driver]Timeout expired

This seems to be related to http://forum.mailenable.com/viewtopic.php?p=53157 and http://www.mailenable.com/kb/content/view.asp?ID=ME020535 but the setups in these links use MySQL as a database whereas we use SQL Server. Maybe this shines some new light on the problem?