In Proton Contacts there is a NAME field and a DISPLAY NAME field per contact.
And in Proton Settings there is another DISPLAY NAME field for your own address(es) (Besides: on top of that, this is APART from ACCOUNT NAME).
This is confusing to me. I don't see the use of a DISPLAY NAME apart from NAME in my contact list.

In my logic the application that is receiving an email should show the DISPLAY NAME that the sender has ENCLOSED in the email (for your own outgoing mail this is the DISPLAY NAME in Proton Settings).

Proton adds new contacts automatically to Contacts with the DISPLAY NAME field filled with the email address.
Proton has the two name fields in Contacts and if you don't fill these fields correctly this causes inconsistencies in various views on contacts while browsing, searching, adding a contact in a concept email etc. And the displayed 'sender name' in the inbox is sometimes not what you expect.

It took me some time to discover what was going on. I hope that you can improve this setup to prevent confusion for users.....