There are plenty of sites that show you how to apply a new SSL cert to your Exchange 2010 Environment. There are a few gotcha's though that quite a few seem not to mention. Here are the ones I ran into when I did this the other day:

1. The SAN Certificate is specific to the machine used to create the cert request, it cannot be imported to any other Exchange servers unless you first export it as a PFX. You must re-key the certificate using a new request from the new server. Back in the 2003 Exchange days, you could just move the *.domain.com cert from one server to another pretty easily. Not so with 2010.
2. During the 2nd part of IMPORTING the certificate using the “New Exchange Certificate” wizard, you must have the certificate REQUEST file (.req) you created in the beginning in the same folder as the certificate you download from the SSL provider. Exchange uses both to format the certificate. 
3. If you have a Forefront TMG Server in front of your Exchange Server, you will need to update the SSL cert on this device as well.
   

The following script will give you a report of all mailbox sizes in the Exchange Organization.

Get-MailboxStatistics -Database "Mailbox Database 1584415394" | Sort-Object TotalItemSize –Descending | ft @{label=”User”;expression={$_.DisplayName}},@{label=”Total Size (MB)”;expression={$_.TotalItemSize.Value.ToMB()}},@{label=”Items”;expression={$_.ItemCount}} | out-file C:\MailboxSizeReport.txt

Note the -Database paramenter, this might change and would be the name of the current database. Also notice the out-file section and the file location. This would be put on the root of the C: drive on the machine running the script. 

When running Microsoft Exchange, all the end-user's email addresses are stored in Active Directory. Some users can have multiple addresses in certain cases. Even groups can have multiple addresses as well. Sometimes you need to find which account gets mail for a certain address. Finding a non-default email address can be pretty time consuming and tedious if you were to right click each one and do properties, etcetera. A faster way is by running an LDAP Query. This can be done in Active Directory Users and Computers.

• Open Active Directory Users & Computers
  
• Right-Click the root of the domain and click "Find..."
• In the upper left click the "Find:" drop down and select "Custom Search"