DEAR GENIUS ! No mail goes out

Dear Genius,

I need your help. I did setup my VPS with virtualmin:<

System hostname “name” ( Operating system Debian Linux 7
Webmin version 1.760 Virtualmin version 4.17.gpl
Kernel and CPU Linux 2.6.32-042stab108.2 on x86_64
Processor Intel® Xeon® CPU X5670 @ 2.93GHz, 4 cores
System uptime 0 hours, 7 minutes
Running processes 60
CPU load averages 0.02 (1 min) 0.03 (5 mins) 0.00 (15 mins)

I’m not able to receive and send mails. I don’t know why. My “linux” friends don’t know how to repair it.
Could you guide me?

Many thanks…

PS: when i check the setup in the home page, the check give me this answer:
Your system has 1024 MB of memory, which is at or above the Virtualmin recommended minimum of 256 MB.
Virtualmin is configured to setup DNS zones, but this system is not setup to use itself as a DNS server. Either add to the list of DNS servers, or turn off the BIND feature on the module config page.

To add to the list of DNS servers …

Click Webmin>Networking>Network Configuration >Hostname and DNS Client and add to DNS servers (its a good idea to add Google nameservers as well and

If your email does not work after doing this check with your server host to see if they routinely block port 25 (port 25 is the only port you can send email).