how to make opera mydefault email programm?

topic says it all. i use firefox for webrowsing and opera as mailreader, but if i click on a email link in ff it opens this crappy outlook. opera is only the default email reader in ie; just cant find the ff-setting for this :\

 

tools-preferences-programs

 

i can only offer tools-options in firefox, but there is nothing email relatedin it, tried this before...