Translation

Hi,
I am translating the file wpmu-fundraising-default.po with Poedit. But when I upload the translated file (together with te .mo file) in the "languages" directory of the plugin nothing happens. I tried to name the file in all this ways:
wpmu-fundraising-default-it_IT.po,
wpmu-fundraising-it_IT.po,
fundraising-default-it_IT.po,
fundraising-it_IT.po
it_IT.po
Any tutorials or any suggestions?
Thank you