For 64bit Windows: HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Mail Enable\Mail Enable\Agents\MTA

• Locate the key name: Pickup Event Class Enabled
• Change the Decimal value to "0" to disbale the COM object.
• Navigate within the MailEnable administration console to: Servers > Localhost > Services and Connectors > MTA
• Right click on the "MTA" node and select "Stop" and then "Start" to restart MTA agent. 

This varies between the antivirus applications , the important thing to do where possible is exclude the MailEnable folders from being checked by your resident Antivirus scanner.  If this is not possible then it should be disabled altogether. Running resident antivirus scanners on a mail server can cause many problems due to the high number of files being moved around by the mail server and subsequently depending on the actions requiring access or blocking access to these files.  In regards to the antivirus, access to these files is required by the MTA and its plug-in's at all times while passing through the service.  This is where the problem of resident scanners inhibit the MTA, while a message is being accessed by the MTA, the resident notices this file access and then does its job by locking the file and doing its own scan while doing this excluding all other programs from accessing the file.

Depending on when the file is locked and how long the scan takes, this will affect the MTA making the occurrences seem very ad hoc some results of this are below;

• some messages with viruses will pass through,
• some will be detected as normal
• blank messages can be delivered to mailboxes
• Messages can appear to get lost in system (really the resident is quarantining or deleting the message)
• In rare circumstances the MTA can crash or messages can become corrupted.

Disabling MailEnable Antivirus scanning

• Navigate within the MailEnable administration console to: Servers > localhost > Extensions > Message Filter.
• Click on "Message Filter" to list the options in the right hand pane window.
• Right click on "MailEnable Antivirus Filter" and select "Disable".

RESOLUTION

As always ensure you are running the latest version of MailEnable which can be downloaded from the MailEnable web site.  For an issue like this it is imperative that you are running the latest.

Once you have isolated the problem then the resolutions are as follows;

Pick Up Events:

If you are the developer of the pick up event then ensure that the pick up event(s) are releasing any files that that are being locked for a completed action.  If the pick up event is deleting then ensure that the delete is occurring.  If the pick up event is supplied by a third party then you should contact them to either contact MailEnable for support or to diagnose and fix the issue.

If you are not sure what the pick up event does or do not need it then you can leave the event disabled.  For Plesk users the pick up event and the COM component are part of the Spam Assassin plug-in to their product so if this is not being used then you can again leave it disabled and use the MailEnable filtering for spam protection.

Antivirus:

You may need to lower the threads on the MTA for your program to run effectively.  The best way to prove this is required is by lowering the threads to one to see if the problem still exists if it does not then you can gradually increase the threads until you determine the best setting for your plug-in.