Supporting multiple Exchange servers and/or multiple Microsoft CRM implementations

A common misconception is that if CRM user mailboxes are spread across a number of Exchange servers, then the E-mail Router must be installed on every Exchange server.  In CRM 3.0, this is not true.

Incoming mail is delivered to an individual user's mailbox as usual.  The Microsoft CRM Rule Deployment Wizard enables a rule to be deployed to each CRM user's mailbox that will forward mail from the user's mailbox to a CRM-dedicated mailbox.  The Router monitors only this mailbox (sometimes called a "forward mailbox" or "sink mailbox") and has to be installed on the same machine as it.

The CRM-dedicated mailbox can be installed on any Exchange server.  The only restriction is that it must be in the same domain (or trusted domain) as the CRM server to enable authentication between CRM and the Router.  The Router should only be installed on the server with the CRM-dedicated mailbox.  Mail can be forwarded from CRM user mailboxes on other servers and even across domains and the internet (as the mailbox will have a regular SMTP email address).

Only one instance of the Router may run on an Exchange server and one CRM-dedicated mailbox can only handle mail for a single CRM implementation.  However, additional CRM-dedicated mailboxes may be created for additional CRM implementations, and the one instance of the Router may monitor multiple pairs.  Only one pair is configured during Router setup, but additional ones can be added using the registry on the Exchange server:

  • Location: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSCRMExRouterService

  • Key: MailboxesInfo

  • Key Parameters: crmServerUrl;emailServer;smtpDomain;emailAccount[;forcedelivery]


    The URL of the CRM server associated with the sink mailbox to read from.


    The name of the local Exchange server


    The SMTP domain name of the sink mailbox.


    The account name of the sink mailbox


    An optional flag that should be set to a value of 1.This flag causes emails to be held in the CRM mailbox until the Microsoft CRM server responds once (then the flag will be cleared automatically). Without the flag, if the Router cannot communicate to the Microsoft CRM server and email will be moved to the undeliverable folder in the CRM mailbox after a number of retries trying to deliver to the Microsoft CRM Server. This flag is useful in scenarios where the Microsoft CRM Server is not available (possibly it is not yet installed, upgraded from Microsoft CRM version 1.2, or otherwise not yet ready to process messages).

Many organizations that run multiple CRM implementations (such as us here at Microsoft) centralize all their CRM-dedicated mailboxes onto a single Exchange server to simplify administration.  

A single user may be a member of multiple CRM implementations and can route mail to them all.  They will need rules that will forward their mail to each implementations' mailbox.

A CRM implementation can accept mail from multiple dedicated mailboxes and multiple Exchange servers.  This tends to be rare as it does not enable many additional scenarios, though is sometimes used for redundancy purposes.  Each additional Exchange server needs to be added to the PrivUser group on the CRM server (as only one is configured during server setup).

- Ilana Smith

Comments (6)

  1. Mitch Milam says:


    Great post. I’m trying to understand the use of the registry key Mailboxesinfo.

    This is a multi-line string type so if I wish to add additional mailboxes to be monitored, do I just add an additional line for the secondary mailbox? Like this:


    Thanks, Mitch

  2. Neil Benson says:

    Hi Ilana, could a Microsoft CRM hosting service provider use this workaround to support email routing for multiple CRM deployments for different customers on a single hosted Exchange server? Anything else we should watch out for in this scenario?

    Thanks, Neil

  3. IlanaSmith says:

    @ Mitch: Yep, new line for each pair of mb/CRM

    @ Neil: Yep, this can definitely be done.  Gotchas:

      *  Deploying the forwarding rule to the end-user mailboxes could get complex if you don’t have access to their mail system (and if it’s not on Exchange), but the rule can be deployed in other ways (imported by user, manually created by user).

      *  Outgoing mail would be sent from the hosted domain, likely spoofing the user domain.  Higher likelihood that it is treated as spam by recipient system if spoofing.

      *  Mail will be forwarded from user mailbox over the internet to hosting provider.  Not a technical issue, but something that participants should be aware of from a security and privacy perspective.

  4. Bhasker says:

    How can we handel Undeliverable emails. We tryed everything they are not coming to crm email account or as an activity.

  5. JP says:

    Hi Illana, will adding a line for a new mailbox/crm implementation in the registry take immediate effect, or does the email router or exchange server need restarting?

    Thanks, JP

  6. Overview: At Microsoft, it almost feels like we are installing a new CRM deployment every week. On the

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