When you use C-Panel to change MX of records to point to CanIt it assumes you no longer want to use it for email and disables it.
(Note this is from a really old piece of -CPanel info:)
From the "MX Entry Maintenance" page set:
Domain MX Entry Always Accept example.com example.com.mf.roaringpengiun.com Yes
Additional information on C-Panel may be found here: