I usually read such messages off-line.
If the message header tells you that the "To" and "ReplyTo" fields are not the same it is a bit of a cluette. If you can't find the header (it will be there somewhere) then:

eg - looks like it is from "fred.bloggs@hotmail.com" but if you clicked on the reply and it was going to "fred.bloggs@yahoo.com" then it is a spammers ploy. Delete both e-mails immediately.

I usually look at hte message "source" in Outlook and that tells you where the Hyperlink is going to. More clues. But if I don't Skype then that is the best clue.