How to block outgoing emails from one email account?

I have a catch-all email account which receives all emails from a domain.

Now I don’t want to accidentially send emails from this account. I tried to set the outgoing limit in E-Mail Mananger/E-Mail Accounts to zero, but it doesn’t allow me to (must be greater than 0).

Is it possible to configure an email account to forbid outgoing emails?

It’s not strictly possible. I could manually add an ACL but it would only prevent it from sending if the matching From address was used, and that’s not currently enforced (monitored for abuse).