A way to block local user?

[rnbwkat]

I have searched and search - no luck. I have a local user that owns a domain. It of course created [email protected] as a username. Now, although it could be an infected WP issue, which I am still investigated, BUT, it seems that [email protected] likes to SPAM [email protected] which is the domain he manages. I have yet to find out where this is coming from, other than it is a local process somewhere. I would love to just block anytime [email protected] tries to email the info account. I can't block it from sending 100% because it is the sender for other critical emails. Any thoughts? Iis there a way to do this?

here is an example of what I am seeing:

2020-02-21 08:00:33 1j58r3-00080o-8T => info-username <[email protected]> F=<[email protected]> R=virtual_user T=virtual_localdelivery S=915
2020-02-21 08:05:53 1j58wD-00086B-P5 <= [email protected] U=username5 P=local S=1284 id=[email protected] T="Subject: ykgkvgzwu" from <[email protected]> for [email protected]

Thanks
Kat