I don't have those kinds of rules. I've ALWAYS had male friends. All the way back to kindergarten. For me, to all of a sudden stop that would be unnatural. If I were may man, I would think something was up if I all of a sudden cancelled those relationships.
My boyfriend of now 4 years, still talks to his women friends. One of those women is his ex, whom I have met. She's cool. I like her. I'm not jealous. I don't feel a way about it, and if I did, I would have to check myself to determine if it's my issue or if he is in fact acting out of character. But to make a rule that they can't have external relationships is stupid. I have married friends who share my point of view and they are happily married and have children in their teens.
This is not a married vs. unmarried issue. It's a people who trust the person they're with vs. people who don't issue.