Of course they can. You can even try it yourself to see what I mean. Highlight an email and then right click on it and select Properties and then Details. It shows all of the details of the email all the way back to the source of where it originated from. If reading between the lines, this is your bit on the side, then you will just have to arrange a secret meeting with them behind the bike shed like we used to do long before the days of the internet and emails. With the advent of modern electronic technology, secrets are now a thing of the past matey!