[tpm]

Would sending a physical letter to their hq be ok?

[ccleve]

Sure, but it's a hassle because you've got to go to the post office and fill out a return receipt requested form, otherwise the letter could just go into a black hole. Plus, who knows how many weeks it would take to get a response?

[dredmorbius]

I'd strongly recommend you accept that level of hassle.

[dredmorbius]

Registered mail, return receipt.