Pls, give me an answer: can MEG work as Internal mail server?
If yes, then how I can configure it?
the short answer to this is no. MEG was never meant to be a mail server. we are an MTA. it is technically possible to do what you are looking for with MEG, but it would require work with secure web mail. beyond that, even if you got the secure web mail part going, you would run out of disk space rather quickly and message retention would not be what it is on exchange. hope this helps.