You can get into nslookup and do the following -

Default Server: which1.tampa.yourdomain.com
Address: 10.160.66.60

>set type=mx
>digex.net
digex.net preference = 10, mail exchanger = zamboni.mail.algx.net
digex.net preference = 100, mail exchanger = dca1-mx.mail.algx.net
digex.net nameserver = nsF.algx.net
digex.net nameserver = nsE.algx.net
zamboni.mail.algx.net internet address = 204.91.99.98
dca1-mx.mail.algx.net internet address = 204.91.241.15
dca1-mx.mail.algx.net internet address = 204.91.241.16
>
>yourdomain.com

you should get the MX information from your domain. If you don't, then you need to add the MX records to DNS.