This article applies to:

• Trustwave ECM/MailMarshal Exchange 7.1 and above (formerly MailMarshal Exchange)
• Microsoft Exchange 2007
• Microsoft Exchange 2010

Question:

• Where are messages queued when the MailMarshal ECM Engine is stopped?
• What are the differences in submission queue behavior (in version 7.1) between Exchange 2007 and Exchange 2010?

Information:

Beginning with version 7.1, MailMarshal ECM introduces changes in message flow.

Different versions of Microsoft Exchange react differently to the new MailMarshal ECM behaviors.

When the MailMarshal ECM Engine is stopped, the MailMarshal ECM Transport Agent will stop exporting new messages for processing (no new messages will be exported to the "Incoming" folder). Regardless of Exchange version, the Agent will "wait" (indefinitely) for the Engine service to restart before continuing to export new messages for the Engine to process.

In Exchange 2010, the submission queue will immediately slow dramatically or even stop accepting new messages. In this situation the "load" is pushed immediately back onto the network (back onto SMTP clients, Exchange Mailbox Servers, Exchange Edge Servers or other Exchange Hubs). Depending on configuration, in larger organizations with multiple Exchange Hubs, this could result in the load bypassing the server affected and being processed on other servers. For smaller organizations with a single Exchange Transport Hub, email flow will stop immediately.

Exchange 2007 will continue to accept new email into the Submission queue. If the MailMarshal ECM Engine is off-line for an extended period, the queue will grow too large and this will force the Exchange hub into "back-pressure". When this occurs, load will be forced back onto the network in the same way as for Exchange 2010.

The difference is in the time it takes for the different versions of Exchange to stop accepting new messages. Under Exchange 2010 the push-back is immediate, while under Exchange 2007 it could take considerable time for the Exchange Hub to stop accepting new email messsages into the submission queue.

Note: In all cases, messages queued for processing in Exchange or MailMarshal ECM are preserved. All messages will be processed when the Engine starts.