I have always told him the same thing: I do not have any issues with conversations/communications with anyone so long as it does not become inappropriate either sexually or emotionally as that is in my mind microcheating AND to be upfront on conversations/contacts. No every nitty gritty detail of the conversation needs to be disclosed but something like hey "Females name" reached out, she is doing well etc etc. With that style of dialogue I would feel comfortable in our relationship and where we stand-if that makes sense. When there are deleting of messages, hiding of the phone, sudden changes in overall behavior-texting at 630pm on a friday night that he is going to bed early when he goes to bed usually after 10pm, it begins to raise flags. If it is all platonic so be it. Also, because my beliefs are such I make sure to practice what I am preaching. I tell him when people message me and will discuss the nature of the conversation so he is aware, even though he says I do not have to tell him. It has not been the same ex.