Mailman was automatically installed on VM installation.
Is it intrinsic to the system, or can it be removed, without adverse effects?
I suppose if you don’t use mailing lists in VM, it should be safe (after disabling the VM feature) to stop and disable the Mailman services.
It might be problematic though to try and actually remove it, since the “virtualmin-base” package depends on it. Stopping the services should do fine I guess, I presume the disk space allocated by the Mailman files is not what is bothering you, or is it? 
I do not use Mailman, but do use other systems, like phplist, which are ‘in domain’.
I do not have any issues here, but it is just a case if it is not needed, I might as well remove it!
Howdy,
I agree with Locutus there, I wouldn’t acually remove it since it’s a Virtualmin dependency. That could cause all sorts of trouble
So long as it’s stopped and not running, it shouldn’t cause you any trouble, it’s not a particularly large package.
-Eric