How to reject bad hosts

[Nicolas Michel]

Hello,

I want to know if there is a way to reject connections from host not 
listed in the MX records of the domain it claims to be.

For example : a host with IP WWW.XXX.YYY.ZZZ try so send a mail to my 
domain (we'll call it mydomain.be) and claims that the sender is 
u...@otherdomain.com

If WWW.XXX.YYY.ZZZ is not a MX server of otherdomain.com my mail server 
will reject the connection.

If it is possible, will it cause some troubles? Will I loose some 
legitimate mails? Because of misconfiguration or an other reason?

Thank you.
nm