Email aliases not deleting completely

We have a series of Virtual Servers all of which were set up by accepting the defaults offered. We are currently running 4.12 Pro.

We service the email elsewhere, but of course, by accepting the defaults when setting up the Virtual Servers originally, we allowed Virtualmin to create 'Mail Aliases' eg abuse@example.com.

To try to improve security of the sites, we want to remove any potential email functionality. We want to do this by unchecking: Virus filtering, Mailman mailing lists, Mail for domain enabled and Spam filtering enabled in the Enabled features section and then clicking on 'Save Virtual Server'.

We have done that successfully for one Virtual Server, but the others say: 'Failed to modify server : A target server must have email enabled if any aliases do'.

We have deleted all the aliases, including the special ones, and, if we go into 'Edit Aliases', we see 'No mail aliases have been created in this domain yet.' This suggests that the deletion of the aliases has been successful, but we suspect that there is some sort of 'hangover' because on Virtual Servers which have no email, there is no 'Edit Aliases' visible on the Virtualmin menu, whereas that menu option does appear on the ones that we are having the problems on.

Is there any way of being sure that all trace of Aliases has been removed from a Virtual Server so that we can then remove its email functionality altogether?

Thanks in advance.