I recently received an email with the subject: Disk Quota usage on system. What does this mean?

First take note of which filesystem the email is referring to.   Here is an example:

Disk quotas for user johndoe (uid 9999):
Filesystem   blocks   quota   limit      grace   files
/dev/sdc1    2862*     2048    3072    7days    1

If the filesystem listed is /dev/sdc1 (or /dev/sdb1 for our Tallahassee customers), as in this example, this is referring to your email space on the server.  Click here to solve the problem.

If the filesystem listed is /dev/sdd1 (or /dev/sdc1 for our Tallahassee customers), this is referring to your home directory space on the server.  Click here to solve the problem.