When talking about the new High Availability features in Exchange 2010 an often recurring question is “How many mailbox databases can you home on an Exchange 2010 Standard Edition?”

The answer is listed here: Looking at the On-Premise Licensing for Exchange Server 2010, and for a Standard Edition you are limited to 5 and for an Enterprise edition you are limited to 100:

The next question is a lot of times: does this apply to active mailbox databases only?

Let’s see…

I’ve got a DAG, called DAG1, which includes two servers: E2010CHM1, and E2010MU2. I’ve created a few mailbox databases as you can see in the picture below:

The following databases are mounted on E2010CHM1:

1. Employees
2. Mailbox Database 0789…
3. Management
4. Soleil
5. Public Folder Database

And the following mailbox databases are mounted on E2010MU2:

1. BHV
2. Mailbox Database 1077…

Now let’s try to add a mailbox database copy for the mailbox database BHV, so it will be available as a passive database copy on E2010CHM1.

Here’s the result:

Conclusion

Exchange 2010 Standard Edition is limited to a maximum database limit of 5 (which is the sum of active and passive database copies, and the public folder database!)

Ilse