It is possible to change the MX records for your domain. For this purpose you should log in cPanel and click on MX Entry.

For more information on how to change the MX records for your domain, please check our tutorial:

http://www.siteground.com/tutorials/email/email_mx_record.htm

SiteGround provides the best email hosting environment and we will help you with any email questions/problems you may have, including MX record changes.