I don't get why protonmail is blacklisted however.
It is the spambot king, most spammers/spambots that get paid use it (goes great with other utilities that I won't mention, but is just as dangerous by itself).
A lot of forums, websites, blogs, etc have scripts you can use/share that won't allow proton and other "10 minute mail throwaways" to be used period and for good reason.