Replay to email address format

Hello,

I have a littile problem here, you see I have an application that sends email to outside email clients example (user@yahoo.com) and the sender (my addres) has full herarquical format example (peter_risdon/Domain@Domain.bluefoot.co.uk)

I know there is a way of selecting a diferent format, say short name only or, first name - last name.

Where is this field (setting)