[rootusrootus]

> feels like you could be sued

As dysfunctional as the legal system seems to be at times, I'd be pretty surprised if she could find a lawyer willing to try that. At the very least, she'd half to pay a fair amount out of pocket just to initiate the suit, and this is someone who already hasn't shown much persistence in just getting the email address corrected with her provider.

A lawyer would presumably tell her that a case against me would certainly fail, and the healthcare provider has much deeper pockets. Go after them.

> How does it work for a paper mail - from what I understand it could be illegal to open any letter originated to some other person's name.

This is a federal law called "Obstruction of Correspondence" and it is fairly specific to USPS mail. It applies to letters & packages that are either in a postal facility (including the mailbox) or have transited through it. It does not apply to email.