Hi,
Look for scripts in Google. There are some available that get all you mailboxes from the server, basically showing what you see in ESM also:
Name, size, items, last login.
If you have small amount of mailboxes/servers, you could do manually in ESM, by opening the mailbox-store, then rightclick and choose export. You can import that into an excel sheet, add a date, do a few times, order on date.
I do an 'average' to see what I am gaining since we recently started archiving deleted items.
Gertjan
Regards. Gertjan