Student or not (and I haven't read the answer posts but I can see those immediately above) this was 2 years before your made vows. Whatever the situation at the time, it is best to realise it is now in the past. If you can't stop letting it bug you then sure, go ahead and risk your marriage, or at least create a bad feeling period, but ideally just let it go. It is questionable saying things that occurred before commitment counts as "cheating". Meanwhile do analyse why you feel the need to snoop in another's e-mails. Either you have an issue, or there is more to this than some old fling that you didn't mention in the OP.