Go to the mailstore properties, and Click on the Database tab. For the Exchange streaming file, click on browse, and select the other drive to send it to.
If this doesn’t work post the error message you get. How much space do you have on each drive?
You should set storage limits on all mailboxes so you don’t ever get to this point.
An offline defrag using eseutil should help you reduce the size of the database immediately. In your case you are going to need to map another drive to hold the defrag temp database. It requires free disk space equal to 110 percent of the size of the database that you want to process. The bottom of the article explains how to use the /t switch to send the temp file to another location. Once you have performed the defrag I would follow mshen’s advice and set mailbox size limits or else get some larger drives to hold your databases.
Also I would not suggest you split the edb and stm files up onto different volumes except as a temporary fix until all other issues are resolved. They work together as one entity and you will most likely experience a huge performance hit. And at the very least do the offline defrag first because you have to defrag the edb and stm together. If you can add drive space and move them both together onto a larger drive space that would be far better. The defrag should help you reclaim enough space to remount the database for the short term. But you definitely need to make plans for increasing drive space and/or setting limits on mailbox sizes.
One web page I checked out states “Each Exchange Server database consists of two matched files: .edb file and .stm file. These files must be copied, moved, or backed up together and must remain synchronized with each other. As database tables are made up of pages, Error – 1018 reports damage at the individual page level. It causes the database to stop or to seriously malfunction.” That is not from a Microsoft web page, but Microsoft Best Practices definitely says to keep these files in the same location.