I would like to see a setting for each email address in the contacts, maybe it is called Email Status:
Normal - Email is used normally
Obsolete - Email is obsolete (the contact changed their email ... to proton!) but is used for identifying older emails using that address, you cannot compose a new email to that address without proton objecting.
Prompt - Email can only be used after verification by the user. For example maybe you don't want to accidentally send an email to your ex-partner or to your boss or someone you have a fraught relationship with. This would prevent that scenario which is one of the banes of email.