Today I find long list of disabled mailboxes in the HC panel under couple of domains how can I remove them all at once in Exchange Server, obviously there is an option to remove one by one but its difficult to remove more than 100 accounts.

List mailbox databases guid
> Get-MailboxDatabase |ft Name, Guid
List disconnected mailboxes in a specific database
> Get-MailboxStatistics -Database <database guid> | Where-Object {$_.DisconnectDate -Notlike $NULL} | FL DisplayName, 
DisconnectDate, MailboxGuid
Delete a specific disconnected mailbox
> Remove-Mailbox -Database “<databasename>” -StoreMailboxIdentity <mailbox guid> -confirm:$false
Delete all disconnected mailboxes in a specific database
> $users = Get-MailboxStatistics -Database “<databasename>” | where-object { $_.DisconnectDate -ne $null } | Select DisplayName,MailboxGuid,Database
> $users | ForEach { Remove-Mailbox -Database $_.Database -StoreMailboxIdentity $_.MailboxGuid -confirm:$false }
ExampleDelete a specific disconnected mailbox in the database named My Database
> Remove-Mailbox -Database “My Database” -StoreMailboxIdentity g437dd12-2f96-4a67-8f6f-c47fa70247e2 -confirm:$false
Delete all disconnected mailboxes in the database named My Database
> $users = Get-MailboxStatistics -Database “My Database” | where-object { $_.DisconnectDate -ne $null } | Select 
DisplayName,MailboxGuid,Database
> $users | ForEach { Remove-Mailbox -Database $_.Database -StoreMailboxIdentity $_.MailboxGuid -confirm:$false }