Even after all these years I still find myself using ⌘Y to try and get a quick preview of a Mail attachment. It doesn't work of course...
Until now. Here's a quick-and-dirty macro to do the trick. Make sure the macro is triggered with ⌘Y, then you just need to put your mouse over the attachment and hit ⌘Y. It's no quicker than Apple's right-click-and-select approach, but it suits my muscle-memory better
And when I say quick-and-dirty, I mean it doesn't have a load of error-checking. It's designed to be used with the mouse over the attachment. I don't think you'll do any damage, but if you end-up sending a love-letter to the boss, don't blame me!
Just in case you aren’t familiar with it, for a selected Finder file and for a selected Mail attachment, pressing the Space Bar invokes Quick Look. I’ve always liked that more than Command-Y because it’s only one key—and a big key at that. Obviously, they important thing is getting accomplished what you want, but I just wanted to make certain the Space Bar method is also known.