In order to enable/disable POP service for a particular domain from MailEnable one needs to perform below mentioned steps:
1) Login into MailEnable Professional.
2) Click on MailEnable -> MailEnable Management -> Messaging Center -> Post Offices.
3) Right Click on domain name -> Properties for which one need to perform the task.
4) Go to the Tab Service Selection.
5) Select the Enable or Disable from drop down menu against POP Service.
6) Click on apply and Ok.