In order to suspend/activate email service from MailEnable interface one needs to perform below mentioned steps:
1) Login into MailEnable mail server.
2) Open MailEnable Professional admin.
3) Go to MailEnable -> MailEnable Management -> Messaging center -> Post Offices.
4) Go the domain for which one needs to take the action.
5) Right click on that domain.
6) Click on Enable/Disable domain.