Summary: Let each contact carry a preferred "send from" alias, so new emails to that contact automatically use the right alias instead of your single account-wide default.

The problem:
If you have many aliases, say one for work, one for personal, and separate ones per service, you can only set one account-wide default sender. Every new message uses that default until you manually change it. With 20+ aliases, it is very easy to forget, which means accidentally emailing a work contact from your personal alias (or vice versa). The mistake is silent and only obvious after you have hit send.

The solution:
A per-contact default sender alias. This does not change how aliases work anywhere else. It just auto-selects the correct alias when you start a new email to a contact who has one set.

How it could work:
- Add a field to each contact's details, e.g. "Send from", with a dropdown of your existing aliases.
- When you compose a new message to that contact, the From field is pre-filled with their assigned alias instead of the account default.
- Contacts with no alias set simply fall back to the current account-wide default, so nothing changes for existing users who do not need this.
- You can still override the From field per message at any time. This only changes the starting value.

Why it matters:
It removes the risk of sending from the wrong alias by making the correct one the default for each relationship, rather than relying on the user to remember to switch every time.