Microsoft‎ > ‎Exchange‎ > ‎

don't see in GUI disabled users

This seems to be a very common complaint from the field - Deleted mailboxes will appear in disconnected mailbox list,
but these changes it will not reflect immediately. You have to wait for
 online maintenance to run and complete before the mailboxes are correctly listed

open Exchange shell and type:

for all database: 

Get-Mailboxdatabase | Clean-MailboxDatabase

or for single database:

Clean-MailboxDatabase MyDatabase