Take the following steps to manually remove EPiServerMail 4.4:
1) Remove every table named tblEPiServerMail*
2) Remove every stored procedure named spEPiServerMail*
3) Remove the folder called EPiServerMail in your site root
4) Remove EPiServerMail.config in site root
5) Remove the episerver.mail section from web.config
6) Remove EPiServer.Mail*.dll from bin folder in site
Additional Note) If you don't have community on your site, you should also do the following:
1) Remove every table named EPiServerCommon*
2) Remove every stored procedure named EPiServerCommon*
3) Remove the episerver.common section from web.config
4) Remove EPiServer.Common*.dll from bin folder in site
Disclaimer: Reasonable effort has been made by the author to ensure that the information provided here is accurate, however, no guarantees for the accuracy of information are made. You hold full responsibility for your actions - please remember to make a backup before making any changes.