well, I don't know. One of my closest friends is a man. We text every day, actually, often multiple times a day. To the point that if I didn't hear from him for more than 48 hours I'd worry a bit.
I also often mention him to my husband, because of course we talk so much that I often mention things he has said to me, as in, X recommended this movie we should watch it etc., so you could say I have mentionitis.
My husband knows him, but they are not friends. If I catch up with him, (he lives in a different city so not often, maybe once a year) my husband and my friend's wife will not come because they find that the interaction is a little stilted, because my friend and I are so much closer than anybody else in the group and share so many interests that the conversation becomes odd, so nobody ends up having much of a good time. They'd rather let us get on with it. But we will do family things together though, and our kids are mates.
I also do online courses with my friend, as we share one particular interest that we pursue through study, and we will "meet" on zoom, usually twice a week and often chat afterwards to comment on the course content.
We rely on each other emotionally, and have no secrets. I wouldn't really show our text conversations to my DH, because I respect my friend's privacy and would expect the same from him. That said, my phone is not off limits, I leave it lying around everywhere and would have no issues with my DH using it.
According to mumsnet lore, we are having an emotional affair and this is all unacceptable. We are not, we are just very close friends, with very similar interests, and have been for more than 20 years. If my DH had a problem with any of this, I would be quite disappointed. As it happens, he does not, he trusts me.
Just a different perspective!