Hosted Exchange Email Forwards and Distribution Lists to external...

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Hosted Exchange Email Forwards and Distribution Lists to external addresses

There are important considerations when configuring email forwards with Hosted Exchange when you have selected the Mimecast archiving option (HE-PRO and HE-MCO part numbers).  If you are using just the HE-STD product which does not include archiving you need not worry about the details covered in this article.

Whilst email forwards and external distribution list members can be configured for HE with Mimecast you need to be aware of scenarios where emails may not be archived when they are forwarded.

A quick summary of the details below is that an email will only be archived if it either flows through the Mimecast email gateway or it enters a users mailbox where it can be captured by the Microsoft Journal agent.  There are some scenarios higlighted below where this will not happen.  First a couple of concepts to understand:


An Exchange journal connector is setup for each Hosted Exchange customer who has purchased the Mimecast Archiving package.  This journal connector captures a copy of emails when they are delivered into a customer mailbox on the platform and sends a copy of the mails to the Mimecast archiving platform.  This allows for internal-to-internal emails to be captured.

Sender Based Routing

Sender based routing is used on a mailbox basis to direct emails out the correct send connector.  For Mimecast customers this is out via one of the Mimecast connectors.  For non Mimecast customers this is direct out to the internet.

Scenario 1 – Email from external address sent to a HE account with a forward to another external address.

- Email sent from

- Email received by Mimecast and added to archive on the way into the Hosted Exchange environment

- Email delivered by Mimecast to Hosted Exchange

- Email does not hit a mailbox and is forwarded straight out to the external forward address (

- As a result of the email not getting delivered into a mailbox because of the forward rule the journal connector does not have a copy of the mail to send to the archive.

In this scenario the inbound mail from Hotmail is entered into the archive when it passes through Mimecast into the Hosted Exchange environment.  The outbound mail forwarding to the external recipient will however not be logged in the archive as due to it being a server level forward the email is external-to-external and had not been delivered into a mailbox for it to get journaled.  Effectively the Hosted Exchange system is just forwarding the email back out with a from address of and a destination of so it has no way to link it to your account.

Scenario 2 – Email from another Hosted Exchange customer to a HE account with a forward to an external address.

- Email sent from to

- As the two domains are local to the Hosted Exchange environment the mail does not go out through Mimecast for delivery but is instead scanned and filtered by Sophos PureMessage for Exchange.

- As there is a server level forward on the mailbox to an external account the email never hits’s mailbox and is direct straight out to

- As a result of the email not passing through Mimecast for the receipt into Hosted Exchange and also not entering a users mailbox the email is not archived.  Note that if the forward to an external address had not been in place and the email had been deleivered into the user’s mailbox this email would be captured by the journal connector and logged in the archive.

Scenario 3 – Email is sent from External address to Hosted Exchange distribution list containing internal and external recipients.

- Email is sent from to

- Email received by Mimecast and added to archive on the way into the Hosted Exchange environment

- Email delivered by Mimecast to Hosted Exchange

- Hosted Exchange delivers the email to the internal mailboxes for which the journal connector will act and journal a copy to the Mimecast archive.

- For the External recipients in the distribution list these are processed very much like a forward and will get sent out as to and will not enter the archive as the email has not entered a mailbox and is not to or from an internal domain.

If you require any further clarification of this please raise a ticket with

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Last Modified:06/06/2014 10:45:04

Last Modified By: stevel

Type: FAQ

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