dual (two factor-auth) gmail accounts in Mail.app Situation: I have two gmail accounts: 1 private (@gmail.com) and 1 google apps (@domain.com) account. Both have 2-factor-auth enabled.

However, the problem is that whenever I restart Mail.app, it asks passwords for both accounts without successfully signing in. Is there any way I can keep 2-factor authentication for both accounts and still get them both to work in Mail.app?
You shouldn't use your Google account password to sign in to a mail app. Instead, use an App Password. That's because most mail apps can't handle a two-factor auth code. For more information, visit https://support.google.com/accounts/answer/185833?hl=en.

You can create an App Password at https://myaccount.google.com/apppasswords