Did he cheat?

Short story.. open relationshiio. Rules: we dont play unless the other agrees to it.. sends me an email saying there a guy that wants to meet up.. i dont get email cuz its in spam (his phone is broke btw) partner goes out of town and he hooksup with a guy even knowing our rule... keeo in mind this is his 3 time meeting this guy i knewe they hooked up once, but the other 2 i didnt know. He gets home we start fooling around does not get hard... So i ask him after i seen email.. did u meet up with him.. says yes... after he said no when he first got home and told me bout email... is it cheating? What do i do? I talked to him he got mad and flipped the issue on me.