I hope this doesn't come accross as a negative thread but due to my own bitter experience, I thought it would be a good idea to share how you can investigate unfaithful partners.
for example, the spotlight search function on iphones/pads. When on the home screen swipe to the right and you can search where a word has been in a text or email (even if it has been deleted). So when I put in sex on my cheating h phone, I was delivered proof!
Keystroke programmes on pcs help identify what they've been typing too.
I am not that I.T savvy, so thought if others could contribute it may help others