> You can both send and receive from them.
This is not quite correct. According to Protonmail:
> but sending emails from a @pm.me email address requires a paid account.
https://protonmail.com/support/knowledge-base/pm-me-addresse...
My criticism is: You should never use an e-mail address from which you cannot send. This has nothing to do with Protonmail but is a problem in general.