I had quite a merry chase through the Exchange documentation this morning trying to figure out the best way to explain something.
Exchange 2010 MailTips come in several flavors. You can set MailTips for individual mailboxes using Set-Mailbox, but most MailTips are automatically generated in some way. You can use the Set-OrganizationConfig cmdlet to control several of these generative behaviors, but there are a few quirks.
One type of MailTips come from data that the CAS pulls from queries against the mailbox server. That’s how the “recipient out of office” and “recipient mailbox full” MailTips work. As long as the CAS can make RPC queries against the mailbox servers, these MailTips will work just fine.
The “external recipient” and “large audience” MailTips rely on data from the Group Metrics component that runs on the mailbox server. Here’s where the quirks start. By default, these MailTips are turned on by default in the organization configuration. However, if you read this you might get the impression that GM data are generated by every mailbox server in the organization. However, if you run Get-MailboxServer and look at the results, you’ll see that the GroupMetricsGenerationEnabled setting defaults to $false.
Where does the GM data come from? That’s the rub. Exchange 2010 always generates GM data on the server that generates the OAB but only if there is an OAB generated. If you use the default Exchange install settings, you’ll get GM data even though it may look like GM generation is turned off. On the other hand, if you turn off OAB generation, you get no GM data until you manually enable GM generation. Neither of these behaviors are documented as clearly as they should be. The “Understanding Group Metrics” topic does mention the latter point, but it took some work to find the topic in the first place. If you do what most admins will do and start searching for info on GroupMetricsGenerationEnabled you’re not likely to find it. Hopefully this will be fixed in a forthcoming update to the documentation.
(Thanks to EJ Dyksen, Nate Waddoups, and Robert Gillies of Microsoft for helping figure out what was going on with this stuff.)