A "Delete" filter works exactly as it should.
I set up email forwarding to another email account and then set up a "Delete" filter. Any email containing "@" in the "From" field (which is basically all emails) are moved to "Trash". I tested it and it appears to work as intended. Emails show up at the forwarded address and are no longer sitting in my yahoo ...
"Is it possible to configure Gmail to reply to forwarded email using the original address?"
Yes. You need to create an alias first.
Go to Settings >> Accounts and Import >> Send mail as: >> Add another email address.
Once created you will find additional options on how to reply to your emails at Send emails from a different address or alias.
I've rejected Gmail because it often misIDs Bugzilla as spam...
Actually, you CAN use Gmail.
Just create a filter for it:
Filters and blocked addresses
At the bottom of your page click on Create a new filter
In the From field type @bugzilla.org
In the next screen choose: Forward it to:, Never send to Spam
You can even create a ...
I ended up just changing their password, removing their recovery phone number and email, making sure that 2FA was disabled, and removing any devices that they had linked to the account.
As far as I know that has completely locked them out of the account including resetting/recovering the new password.
Then I logged into their email and setup forwarding to ...