Besides disk consumption, when a software does not behave as it should, one wonders if there are any other complications during installation/configuration.
Also the whole point of having a control panel for host management is to avoid doing anything manual as much as possible.
After installing Plesk 17.8.11 on Windows 2016, with SmarterMail Enterprise 13.6, we noticed that after deleting a domain through Plesk, the relevant SmartreMail folder gets renamed to domain_name.ext.disabled, but it does not get deleted.