Restrict certain mailboxes to a few MTAs

[Jeroen van Aart]

I was wondering if there is an easy way for postfix (debian lenny) to 
restrict a few mailboxes to only allow a specific list of MTAs to be 
sending email to those recipients. Ideally I would like to have this 
list in a format like x.x.x.x/xx.

Thank you,
Jeroen