(Exchange! Powerful! Best-of-breed! Most reliable email solution! AV and Spam filtering included with all Exchange plans.)
Managed Web-Only $4.95/mo
2GB Email Storage, Web-Only interface, no ActiveSync to phone--use web interface on phone. No contact/calendar sharing!
Managed Exchange $8.95/mo
Unlimited Email Storage, ActiveSync up to 5 devices, plus MAPI, IMAP, POP3, contact/calendar sharing, unlimited resource mailbox, NO Skype for Business.
Managed Exchange Plus $12.95/mo
Same as Exchange but you can ActiveSync up to 10 devices, and Standard Skype for Business is included. Enterprise Skype for Business is an available upgrade.