webmail domain error

Hi friends i need your help for webmail.
untill now when i wanted to check the emails i wrote https://www.mydomain.gr/webmail but since some days ago when i wrote https://www.mydomain.gr/webmail i got error 404 and i noticed that now i have to write webmail.mydomain.gr in order to get access to webmail.

Does anyone know how this happened? can i change it back to https://www.mydomain.gr/webmail?