You can use Microsoft 365 admin center or Windows PowerShell for deleting Exchange Online mailboxes. The effect of deletion on the mailbox varies according to the process used. Soft-deleted user-mailbox is that mailbox which is deleted via Microsoft 365 admin center or using cmdlet in Exchange Management Shell. This mailbox still will be residing in Azure Active Directory recycle bin for less than 30 days. Also, the mailbox is termed as soft-deleted if Azure active directory user account related with user mailbox has been hard deleted. Or, if user mailbox has been soft-deleted for more than 30 days, or the related Azure active directory user has been hard-deleted, the mailbox gets deleted forever and is termed as “hard deleted mailbox”. This in turn means if the soft deleted mailbox survived the default 30 days retention period in the deleted folder or it is deleted manually, it would be deleted permanently (hard deleted).
You can delete Exchange Online user mailboxes in two different ways:
The easiest method to delete a user-mailbox in Exchange Online is by using Microsoft 365 admin center.
If you delete a user account in Microsoft 365, the related mailbox from Exchange Online gets deleted. And the user account in Microsoft 365 gets listed in the Deleted Users page in Microsoft 365 admin center. This user mailbox can be recovered within 30 days. After this time exceeds, it gets permanently deleted and cannot be recovered.
This is how you can delete user mailboxes in Microsoft 365:
Similarly, you can delete user mailboxes one-by-one. After deletion, to stop paying for the license assigned to the deleted user-mailbox, you need to remove its license. To do this, go to Microsoft 365 admin center. Then, navigate to Billing>Subscriptions; select the subscription and then choose Add/Remove licenses to delete the license and stop paying for it.
You can permanently delete Exchange Online user mailboxes using Windows PowerShell:
To view the user profiles residing in your deleted folder (as it resides in the deleted folder for 30 days period), run the following command:
Old and outdated user mailboxes are always undesirable and should be properly disposed of. These two easy methods provide solutions to get rid of unwanted data. Although, if you want to back up your Exchange Online mailboxes before deleting them, trust Kernel Office 365 Backup & Restore tool. It is an advanced Microsoft 365 Backup tool to back up Exchange/Microsoft 365 mailboxes and import PST files to Microsoft 365.
This article suggests two manual ways to perform soft as well as hard deletion of user mailboxes. However, it is recommended to back mailboxes before deleting them. For this, a smart Microsoft 365 backup tool is recommended in the end.