smtp and a fake domain

Have to borrow some insight here.............. The easy parts were getting dns, apache, ftp, all running by reading and doing but before I tackle sendmail is it possible to have an email account on an isp and use a linux box at home as an email server...........? if so or not can someone answer/point in the direction I should look to research this and implement it........ I have a small lan at home w/6 boxes and migrating from windows just haven't got around to purchasing a domaine name as of yet so seeing how things work before hand... It would seem I could use my own email server with a mx record pointing to it by need some pointers or info......this is a little bigger cryptic looking monster than the rest of my projects thanks much