Hey, I don't mind if you ask it of course! I think it depends on which culture you live in tbh, so that's why I have this perspective. Around me, it's not common to have friendships of the opposite sex when you're in a relationship. Even if you trust your partner, there's always a possibility that you can't trust the other person outside your relationship.
First of all, he never had any female friends when we started dating except for one girl. However, a lot of people warned me for that girl (which is a classmate of his), because she is really flirty, fake and fake nice as in: she gains your trust, you tell her your secrets and she spreads those. She is a major bish to girls, but to guys she tries to be as sweet as possible etc etc.
I don't want a person like her invading my relationship with my boyfriend, but I only found out about her after they went to eat dinner together even though we were dating and he told me about it afterwards. I was really mad about it for like a week, because he should have asked me before hand and we never dine outside together. He said that she's just a classmate and the whole dinner was actually him talking about me.
For me, this was a major red flag, because he told me she asked a lot of questions about me since she didn't knew me and the main topic of their dinner was me. Later on, I asked a guy friend who is also a good friend of my boyfriend and he said that that girl is very mischievous (he told me some examples of what she did to people) and that I should avoid her in every way, but my boyfriend is to naif and innocent to see that, he thought she was simply interested about me. I told him about this and ever since then, they haven't talked to or met up with each other.
Next to my boyfriend, I actually do have a lot of male friends whom I know for years, but I restrain myself from meeting up with them alone. They are allowed to text me and my boyfriend is allowed to see my texts if he wants to, even though we never ask about our messages to people, because we trust each other in that perspective. I don't meet up with them solely, because in all my relationships so far, a lot of rumors have been made up and people (friends, haters and acquaintances) tried to destroy my relationships. Plus I think it's unfair and my boyfriend won't like it if I would hang out with another guy or a group of guys. Guys will contact my boyfriend and make him feel jealous or have less trust in me. I remember also that one guy changed his profile picture of him with me just to make my boyfriend jealous.
I have an example of when I was single; it was raining very hard and my male best friend and I were sharing one umbrella after shopping. A guy from my school saw us and every time when I saw him, he kept asking me if my best friend really wasn't my boyfriend, because we looked so close and lovely together. Imagine if I had a boyfriend, he would only have caused trouble.
This best friend is still one of my best friends and recently, he asked when he's going to meet my boyfriend and me again. I don't want him to meet up with my boyfriend, because they have both very different personalities (my boyfriend is very shy and barely talks around people he doesn't know) and my best friend and I share some of the same hobbies my boyfriend does not have. I'm afraid that while talking, he'll feel out of place and sad. My friends and the people I know are between the age of 20 and 30.
My boyfriend knows about all me. For example: My first real boyfriend cheated on me with my best friend for some months. My ex who also used to be my best guy friend, still flirts with one of my best friends whom he met through me. My last ex met óné guy friend of mine and immediately could see through him that he had feelings for me, which I couldn't see at that time so in the following weeks, he kept making remarks about him and asked if I had contact with him. I had a Spanish summer boyfriend, but one of my male best friends kept saying stuff about me to him which made him very jealous and broke up within 2 weeks and afterwards sending me a sorry e-mail and he stated how much he hated my old best friend (lol). Guys in my class who have relationships for years, but cheat almost everyday. My cousin her ex-fiancee went on some dates with her best friend and her ex-fiancee told my cousin about this instead of her best friend. etc etc etc
From my experience, in my relationships it's healthy when I keep relationships and friendships separated and most of my friends do the same thing. The ones who don't always tell me about their dramas with other people in their relationship. There's a saying here: Keep your boy/girl friend to yourself, don't share him/her with others.
tl;dr Boyfriend only had 1 female friend. Female friend was actually a fake friend. I have male friends, but only have contact through text so I do not meet up with them, because people make up rumors and cause drama. In the past, had breakups and know about other breakups because of other people. In my culture it's not used to have a friends from the opposite sex when you're dating, if you do, you will have regular drama because of them.