Bulk Clear in Gmail
Mass-select all or specific emails
Click on the 'Inbox' section of Gmail
Enter in "in:inbox" in the search bar — this will return all emails from all categories in your Inbox
Type "before:yyyy/mm/dd" in the search bar to filter all emails before a specific date. (i.e. in:inbox before: 2022/07/01)
Tick the empty box at the top left, under the 'From;tab
Click the "Select all conversations that match this search"
Bulk Clear in Office 365
Do a mass selection in Office 365 OWA (Outlook Web App)
Select one email and then hold down the Ctrl key to select other emails.
Click ‘move’ on the right side to move these selected emails to the archive folder.
Select one email and then navigate to the last email, and then hold down the Shift key so that you can select all the emails.
Click ‘move’ to move them into the archive folder.