Can I password protect Apple Mail and/or individual mailboxes?

Multiple mail accounts work just fine.

Apple mail mailboxes cannot be password protected.

Mail messages can conceivably be forwarded to a different email account, but that’s not without its own issues.

Mail accounts can be marked as offline within mail, but that’s not a password-protected operation.

I don’t know of a way to cause mail to prompt for the mail server password for each connection.

If an untrusted second party has access to your Mac and to your Mac login password, you’re already headed for deep trouble and well before any discussions of mail.

Probably the closest option with only the default tools is a second Mac login with a second and parallel mail configuration.

So… what issue are you trying to address here, in general terms? In terms of security, SMTP mail leaks metadata all over the place, so isn’t the best choice for really sensitive data.

It is not clear what it is you are trying to do. Your Mail app will not run until you log in with your Mac password. So by default it is password protected. Then, each email account is password protected. You can run multiple email clients but I'm not sure that does anything about your passwords and the protection you are asking about.

d_lee wrote:

I'm wondering if there is a way to password protect the Apple Mail app - or - password protect individual mailboxes within Apple Mail. Alternatively, is it possible to run two separate Apple Mail apps at the same time?

thank you in advance!

One Apple Mail Application and multi- accounts is possible all within the one application is doable. More than one Client Application for mail is also doable.