If a message is deleted from your trash, it will be permanently deleted from Gmail. Residual copies of deleted communications and accounts may take up to 60 days to be removed from our servers. Deleted messages may also be kept on offline backup systems for a period of time.

Go to the folder you want to be cleared. Select the check box above the message list in the reading pane. Select Empty Folder from the drop-down menu in the reading pane. Your email will be moved to your Deleted Items folder, where it will be deleted permanently after 30 days.

Emails that have been deleted are recoverable for 30 days, but they can only be found by an admin using a Discovery search in Office 365.

When there are no new emails: Select ‘Compact’ from the options menu that appears when you right-click on Inbox. Empty and then compact the ‘Junk’ folder. Compact the ‘Drafts’ folder. It sounds like you have some corruption in your Inbox if your deleted emails reappear after every update. As a result?

If you’ve permanently deleted an item in Microsoft Outlook or Outlook on the web (formerly known as Outlook Web App), it’s placed in a folder (Recoverable Items > Deletions) and kept there for 14 days, by default. You may change how long items are kept, up to a maximum of 30 days.