Exchange Catch All Creation

Exchange 2000/2003 Catchall Mailbox Script package

Summary

This package contains the necessary files to allow an Exchange Administrator to install a "catchall" email address for an Exchange email domain.

A "catchall" email address is an address that receives all email for a domain that is not specifically routed to a mailbox. For example, if this package is installed for "@domain.com" and an email is received for "dummy@domain.com" and "dummy@domain.com" is not assigned to a specific user (or public folder) in domain.com, then the email is routed to the catchall email address.

A catchall email address may be to a user's mailbox or to a public folder. It should be local to the Exchange server this package is installed on.

Warranty
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No warranty, express or implied, is provided. This code is provided "as is". It works for me, it may or may not work for you.

Install
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Create a directory on the Exchange server where the package is to be installed. It should be the Exchange server which receives incoming Internet email. The script files included with this package presume that the directory will be C:\ExchangeScripts.

If you do not install the files into C:\ExchangeScripts, you will need to edit the file Catchall.CMD to specify the full path to the script file.

The file CatchEmail.vbs MUST be edited to define appropriate constants for strEmailDomainName1, strEmailDomainName2, and strDestinationEmail.

The constants strEmailDomainName1 and strEmailDomainName2 define the domains to be examined for the catchall destination. If you have only one domain of interest, then define the two constants to be the same.

The constant strDestinationEmail is the catchall mailbox address. It should be local to the Exchange server this package is installed upon.

The required format for all three definitions is provided by example in the CatchEmail.vbs file.

Also, the constant bDebug may be defined to true or false to provide debugging and status information in the Application logfile of the Exchange server. By default, it is set to false.

Once the CatchEmail.vbs file is edited and saved, execute the "Catchall.CMD" batch file to register the script with your Exchange server. That's all it takes.

To remove the script, execute the "RemoveCatchall.CMD" batch file to un-register the script.

Discussion
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The lack of a catchall email address in Exchange is difficult to deal with in a hosting environment. It's a common feature in Unix email systems and in other Windows email systems, but is not present in Exchange. The need to provide this capability was the impetus for authoring this package.

This actually represents the fourth rewrite of the package. As my understanding of LDAP, Active Directory searches, and the performance impact of various solutions changed, thus did this implementation.

On my hardware, an incoming email to a domain not of interest is delayed by 0.05 seconds on average. An incoming email to a domain of interest is delayed by 0.09 seconds on average. For my environment, this is acceptable.

The implementation uses the CDO.SMTPOnArrivalSink method exposed for scripts. The implementation therefore runs under the inetinfo.exe process and is synchronous. On an extremely busy Exchange server, it is POSSIBLE (according to various Exchange 2000 experts) for this to cause inetinfo.exe to miss an SMTP connection and thus delay (or even possibly lose) an email. No one has actually reported that to occur. However, you are now forewarned.

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