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The pros and cons of 'catch-all' Exchange Server mailboxes

SearchExchange.com contributor Serdar Yegulalp explains what a catch-all Exchange Server mailbox is and the pros and cons of using one. He also shares a script that can automate the catch-all process for a given domain.

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Catch-all e-mail addresses are mailboxes that receive messages for a domain that do not match any specific address in that domain.

For instance, if someone sent an e-mail to [email protected] when no such e-mail address existed, it would get routed to a catch-all address for the utena.org domain. If no catch-all address was set up, it would simply be bounced back to the sender with an error.

For a long time, catch-all addresses were immensely useful. When e-mail was still relatively new, a domain could use a catch-all address to make sure e-mail with a slightly misspelled mailbox name could still make it to the intended recipient.

This required having a human attendant periodically check the catch-all mailbox; most of those duties were usually assumed by the e-mail administrator or a personal assistant.

The rise of automated spamming has made catch-all mailboxes lose favor with many e-mail administrators, since they can wind up catching more spam than genuine e-mail. A common spammer tactic is to send flurries of messages to randomly generated or dictionary-harvested names for a given domain. If that domain has an unprotected catch-all mailbox, it will get choked.

That said, there are still mail admins that like the idea of a catch-all address, and if combined with proper filtering and validity checking, it's possible to keep a catch-all mailbox relatively free of spam.

Exchange Server expert Michael B. Smith has written a script for Exchange 2000 and Exchange 2003 that performs catch-all functions for a given domain. The original version of the Exchange Server script proved to be immensely popular despite some limitations -- for instance, it originally couldn't handle more than two domains at once. Smith has since revised the script to add that and other new features.

The script package includes detailed instructions for installation and configuration. Administrators have to provide definitions for each domain to be trapped, but little more than that.

Smith also has tentative plans for an Exchange 12 version that uses managed code and may run much faster, although the current version doesn't impose more than negligible overhead.

About the author: Serdar Yegulalp is editor of the Windows Power Users Newsletter.


Is there a script for automatically deleting e-mail that may be caught by the "catch-all" mailbox?
—Roy P.


I did a little digging and found a script in Glen Scales' blog that might do the trick for you. This script crawls a mailbox and deletes everything more than x days old, which ought to be perfect for a catch-all mailbox that you don't want retaining mail of more than a certain age.
—Serdar Yegulalp, tip author

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  • Reference Center: Exchange Server scripts and programming tips
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