If it's just an Option that can be checked and unchecked, then the hackers will disable the option when they are using victims' accounts to send messages just like they would u check "save copy to my inbox"
My suggestion is that maybe we have the account automatically locked when there is a sudden change in the IP address log from the usual pattern accompanied with a verification email with information about a mandatory security check.
2FA will not be implemented on this forum software. Maybe on the new forum software. This has been suggested multiple times but nothing has been done.
I already thought about hackers disabling the option.
Also, an e-mail notification would be sent whenever someone decides to opt-in or opt-out.
If a hacker was trying to cover his tracks by disabling, sending PM and then enabling again, you would get 3 e-mails. It would probably be better if someone had the option of getting a text by phone. However, I'm not sure this is possible, or if this site even wants to store something as sensitive as a phone number.
How about the option of making the "save a copy to my outbox" a default setting that can't be changed and message saved in outbox can only be deleted after certain number of days like 30days period.
Some people may not want a certain PM stored in their outbox for any period of time. They may want to convey some personal information that they also request the receiver delete when they are done with it. I realize there are better ways to go about this, though.