Immediate idea is to make the files immutable, But given how this patching works I imagine they don't account for error handling like that and may break sending mail as well depending on what their script does.
Hi,
I had the unfortunate experience of a client requesting Plesk installed.
After setting up postfix, disabling mail on plesk, Plesk WITHOUT ANY INPUT OR CONFIRMATION OR WARNING, overwrites this production servers postfix config every morning during patching, changing the destination address...