Gmail – Can you disable Gmail but still hold the address to prevent impersonation

Plus sign is GMail's delimiter for aliases, which many people use for filtering and tracking spam.

For example, you want to make sure that your bank's emails are all legitimate so you'll register your email with the bank as johndoe+mybank@gmail.com and then create a filter that deletes all emails that don't match from:MyBank AND to:johndoe+mybank@gmail.com. Alternatively, when you register with a shady site you can provide your email as johndoe+shadysite@gmail.com and then create a filter to delete everything that is sent to that address.

However, beware that some sites have poorly-written validators on allowed addresses, which block emails with plus sign, which is actually an allowed character per RFC 5322. Google doesn't allow it simply because it's a reserved character in their system.

On Android:

1. Open the Contacts application
2. Press the MENU key then Accounts
3. Click on your Gmail account
4. Uncheck Sync Contacts

Then in a web browser:

1. Open Gmail
2. Go to the Contacts workspace
3. Delete all contacts, page by page.

Gmail will still expand in the Android app, but there at least you can modify the To: line manually.

(Huge thanks to derobert for the tip!)

Related info: https://support.google.com/mail/answer/1311182?hl=en