e-mail address case sensitive

I have an e-mail address like

Name.surname@server.xx but if you send me a mail with address

name.surname@server.xx I can't see it on Mac Mail, but I can see it if I go direct to the server.

I have had to set up two mail accounts, one with the upper case address and a second account with the lower case.

This then presents another problem in that only one address will be picked up by the all inbox tab in Mail. The second account has to be searched by drilling down through the inbox tabs.