the biggest black pill recently was trying to use proton mail to sign up for an email alias product and getting a message IN PROTON saying "this email was used for a third party service sign up but this account is restricted" - proton actually withheld delivery of the welcome/confirm email!

to reproduce: create a new proton account with an lnemail.net address as the collateral they demand at sign up. then once created, immediately use the proton account to create an anonaddy.io account.