My H and I have a sort of don't-ask-don't-tell policy. I don't date anyone who he doesn't know about, but I don't go into detail about dates, or what we do or anything else. Right now I'm actively looking for another partner, so I'll tell my H that I have a "meeting date" for drinks after work, but we don't discuss them. He'll ask me in a general way "how did it go?" and I'll respond in a very general way ... "nice guy, but we prob won't go out again" or "I liked him, we'll see" or whatever. But I just don't go into detail.
Ok, all of that said, if I've sent something to my guy that makes me smile, I won't cc it to my H or send them both the same thing in the same email. I will write a separate email to each of them, even if it takes me a few more minutes to write two emails than to do just one.
I NEVER send affectionate messages to both of them in the same words. For me, anything affectionate or loving is about what *they* represent in my life and not something I can express to both of them in the same words.
Also if my guy sends me something funny or sweet or cute or whatever and I think my H would like it, I'll copy and paste it into a new email to him, rather than just forward it.
Maybe some people find that overly careful or overly paranoid, but given that my H is not involved in my relationships with others, I want to be as respectful of him as I can. I want to make sure that he's never put in a position to feel that he's playing second fiddle to whoever I'm dating (especially since we have a different sexual dynamic and so it would be easy for him to feel marginalized in other ways).
Obviously, as with everything, the disclaimer is that this is how I manage *my* relationships and how it all works for me/us.