Hi,
Please make sure that the account and password details entered are correct.
If this is continuing to be received, please check the status of the LDAP server. From the web GUI, please check the communication between the IronPort and the LDAP server. You can run this via the following:
System Administration > LDAP > (click on) LDAP_SERVER (under 'Server Profile') > (click on) 'Test Query'.
Also, the ESA will maintain a number of active TCP sessions to your LDAP servers. These will be used for 6 hours or 10,000 queries, whichever comes first. What can happen is that a TCP session can remain idle for some time while mail flow is slow. When the ESA attempts to re-use that connection, your firewall may see that this TCP session has not been used for a long time and so it will drop the packet.
To correct this, you would need to disable the TCP idle timeout settings on your firewall for the ESA's IP address. Additionally, please check idle timeout settings for the LDAP server software (i.e. Active Directory) as well as any related settings on the server's software firewall.
I was also able to find below enhancement bug articles which can be the cause of the issue, you can plan to upgrade your ESA to the latest Async OS versions:
https://bst.cloudapps.cisco.com/bugsearch/bug/CSCun98077
https://bst.cloudapps.cisco.com/bugsearch/bug/CSCvo27027
I hope the above information helps!
Cheers,
Pratham
