What if i did someone wrong after i found out they lied to me about having with a friend? ?

I was friends with this guy a while back when i use to work with this guy but i ended up having a one night stand and lather developed feeling for a guy who was not my boyfriend but then lather on down the line i realize that I do love my boyfriend and i made a hugh mistake. But i realize that the guy i had a one night stand also fooled around with a girl i used to work with and lied to me about doing anything with her so i told her that he was no good in a text message but she never knew it was me who sent it because it was from a different phone she could not track... I never told her it was me but I do wonder now that i took the wrong approach on things and i should of went to him and not her now he knows i hate him and it has been almost 5 mouths since we talk.... so i threw everything out his # and never contacted him again because of what he did now he sends me a e-mail that states do u still hate me should i reply? and tell him no I am sorry....