If your company needs email, rather than set up your own email server, consider using the Google App Email service.
The service allows you to bind create email bound to your domain name that are then handled by google mail. For example, with our domain name earth.com we could have email addresses like,
clark.kent@earth.com
loise.lane@earth.com
The Google App Email service is free for up to 10 accounts.
Update: No longer allows give 10 free accounts – However there is a workaround to get 1 account http://www.hongkiat.com/blog/google-app-mail-for-free/
Besides not having to deal with the overhead of running your own email serves, Google Email also has support to 2-Factor Mobile SMS authentication through Web Browsers and a form of OTP when connecting devices or email clients. Consider turning this on for high security accounts.
Google Apps Control Panel
Log into your Google Apps making sure to replace earth.com to your actual domain name,
https://www.google.com/a/earth.com
Click Settings.
On the left hand menu select Email.
Click Change URL.
Select the second option marked (custom) which should look like,
http://mail.earth.com
Click Continue.
At this point you will be given instructions to update your DNS provider with the CNAME record.