By default (when this is set to No), Virtualmin will not delete any mail aliases in a domain when the email feature is disabled. This means that if email is ever re-enabled, aliases will be restored and users who had email addresses before will have them again.

However, when using Postfix email sent from the Virtualmin system by the `mail` or `sendmail` commands will still be forwarded to local mailboxes if these residual aliases exist. If this is causing problems for you, this setting can be changed to Yes before a domain has mail disabled, to ensure that aliases are fully deleted.