Yes, you can only reply to emails you received via hide my mail, but cannot compose new ones. This is a dealbreaker for some use cases, but the potential for abuse is understandable.

I use Hide My Email whenever I can, and then use custom domain name for official stuff. Works really well.

The only annoyance is you cannot send emails from the email aliases directly, you can only use it when replying to an email received on that alias.

I hope this rolls out worldwide. Look Up in photos is not available in my current region unfortunately.