Open your email inbox
Select all messages in the current view
Look for an option to select all conversations in the folder
Click Delete or Trash
Empty the Trash or Deleted Items folder
Repeat for other folders such as Promotions, Social, Spam, Sent, and Archive if needed
If using Gmail, select all conversations in the inbox, then choose Select all conversations in Inbox, then delete
If using Outlook, use Select All, then Delete, then empty Deleted Items
If using Yahoo Mail, select all emails, then delete, then empty the Trash
If using Apple Mail, select all messages, then move them to Trash, then empty Trash
If using a mobile app, use the Select option, choose all, then delete
Check for any remaining mail in folders and delete them too
Confirm permanent deletion if prompted