Paste

If you copy an address to the windows clipboard and hit the paste button - - it will be pasted into the address box

If you have a suspicious looking set of email headers you can copy them to the clipboard from your mail reader and paste them into Sam Spade using Edit → Paste or the paste button - . They'll appear in a new window, with any addresses highlighted as active text.

If you have Smart Paste enabled Sam Spade will run a rudimentary header analysis. It's not perfect, but can sometimes find suspicious parts of the header

You'll need to paste full headers for header analysis to be useful