It used to work just fine, but now it stopped forwarding registration/email confirmation emails. Well, it says that it forwards them (the "Forwarded" field is incremented), but no emails arrive in my inbox. Surprisingly, pure-text emails from my other email addresses arrive normally.

Reply 1: I use ProtonMail. And yes, I did check spam and trash and every other folder - it's not there. Also, pure-text emails stopped getting forwarded too :(

Late edit: works perfectly fine now.