[mattpallissard]

One of the common spam flags are email addresses or names similar to yours or your affiliates.

[Mistletoe]

It was a totally different name. It just didn't like the Proton domain and this is extremely uncool because all the emails I've gotten from Proton users in the past were definitely not spam and were all authentic people. I can't say the same for Gmail.

[Fatnino]

Remember when Gmail was new and you needed an invite from an existing user to create an account?

Yahoo mail was tossing those invites right into spam.