Jan 16 2021 03:23 AM
Jan 21 2021 04:42 AM
Database size on disk will never reduce by removing mailboxes.
If you have deleted the mailbox then after 30 days (by default) the detached mailbox will drop out of the database and Exchange will release the internal space back.
If you have completely emptied the database of mailboxes then you could dismount the database, delete all copies and re-mount database which will recreate about 256MB of files.
If you can't remove all mailboxes then best bet is to create a new one and add any new mailboxes to that. The old database should at least stop growing after 30 days once it purges the old mailboxes.