[RKDinOKC]

Host a full featured email server, calendaring, contacts, etc. activesync for phones, downloadable full email client that matches webmail client, and backup/archiving. Cost of Internet and keeping server (replace every 3 years), email software, and hosted antispam up-to-date is just under $5/mo for 30 users. Have had this server setup for over 11 years. Pay a little more for anti-spam hosting as opposed to running anti-spam on my server because it keeps the spam traffic off my internet bandwidth. It's like the $4/mo 365 exchange account, only I provide a client and anti-spam. Also provide ftp that works like Drop Box.

enom charges $14/year .com domains, and $1/mo basic email. so $26/yr for .com domain and 1 email.