I would like to see an option that allowed me to make message expiration the default for all my new sent emails to other Proton users. This would make a person choose to take action if they wanted a message to not expire.

An addition to this might be to allow a default to be set for each email address that I send to. For example, I could make the default for message sent to grandma to not expire, but make the messages sent to my business partner to default to expire in two weeks. It is sometimes good to know that messages are gone and cannot be retrieved.