Microsoft 365 Email close to limit

Hi @BM 
Thank you for reaching out to Microsoft Learn Q&A!  
Based on your description, I understand that you would like to permanently remove deleted emails before the standard 14-day retention period. 

According to the referenced image below and the article https://learn.microsoft.com/en-us/exchange/recipients-in-exchange-online/manage-user-mailboxes/change-deleted-item-retention#more-about-deleted-items-and-retention-time, your intended outcome should be fully achievable without issue 
To return storage, you only need to take one additional action: delete the items once more from the Deleted Items folder. You can do this by using the Delete option in the Home ribbon, or right-clicking the items and selecting Delete, or using the Shift + Delete shortcut to move items directly to the Recoverable Items folder. 

If you wish to permanently delete these items, simply select the ones you want to remove in the Recoverable Items folder. To navigate to Recoverable Items, please refer to the illustration below

You can select specific items or use Ctrl + A to select all, then click Delete in the Home ribbon to remove them. 

I sincerely hope this information partially clarifies your situation and assists you in planning your solution. Please do not hesitate to reply if you have any updates. 

Thank you for your understanding. 

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