Please make sure you use all of the following MX records and replace "domain.com" with your domain. Please be sure that these are the only mx records you are utilizing and make sure the priorities are as defined below:
domain.com. 3600 IN MX 10 domain.com.mx1.intertune.com.
domain.com. 3600 IN MX 10 domain.com.mx2.intertune.com.
Note: Please make sure both of the mx records are assigned the same priority.