Accessing email via dns service

Hoping someone can throw light on this issue for a Linux newbie. I'm running Ubuntu Server 12.04LTS and accessing the web via DHCP client on a Netgear router/modem. DNS service is provided through Dyndns.org Basic website is accompanied by a Moodle site which is the main focus of my operation. (support learning and teaching for U3A group) All features and functions of Moodle are operative however email cannot be sent or received. My previous experience with Moodle sites has not relied on this DNS service and I have no idea what influence their operation has on the handling of email. If someone is familiar with all the links in this chain I would appreciate some explicit advice. Cheers, Rob