This is adapted from a post in a discussion on a message board.
My thoughts on friendships between males and females. Mostly my experience.
One thought that comes to mind is that bisexuals manage to have friends. And homosexuals have same-sex friendships. That suggests that a "no it can't work" is too simplistic.
Though socialization makes the male female dynamic different than those.
The brief generalization would be, yes, friendship between a man and a woman outside a romantic/sexual relationship is possible, sometimes a very beautiful friendship, but good boundaries are needed.
There's variation though. My guy friends aren't people I call up to get together with individually. I don't make plans to see them outside of where I regularly see them. It's not that I don't have contact information. But I don't often use it. It's not something I planned out that way, for my friendships with guys to be like that. But it's how it's worked out.
(Note that the not using contact information doesn't apply to internet friendships. I'm talking in-person ones. On the internet, pretty much gender/sex doesn't make any difference for me.)
Also, with friends where there is a significant attraction, I don't think those would work as one on one friendship. But in a social situation, and with freedom to not interact when attraction feelings are strong, I've had some pretty meaningful friendship happen.
Some guys there's not much if any attraction there and it's really not an issue. That might be different with more time spent with them. Or maybe not. Depends on the guy, and the boundaries in the relationship.
I have one friend who for a while I used as someone I could share stuff on my mind with by email. Sometimes he emailed back with advice. (Yeah, an exception to that not using contact info much. Although, really, not used much, actually.) I wouldn't say no attraction. But little. But it's also not a friendship where it's someone I hang out with all the time.
I've one friendship with a guy where there's been a lot of attraction at times, and yet, other times it's not an issue. One thing that's made it work is there was a lot of respect for each others feelings, and a lot of space. And a lack of flirting. I'm not against some playful flirting, but in this friendship, it would be wrong.
On the other hand, I've another friendship where I do sometimes flirt. He's someone I've come to be able to be very relaxed with, and free to share whatever thought comes to mind. This is always, though, in a social context. Not a getting together just to see each other.
And then there's the one friendship where it's all been pretty messy, and I've pretty much, for now, given up trying to make a friendship work. So sometimes it doesn't work out so well.
I'm glad for my guy friends. The single ones respect that I'm married and loyal to my husband (or just aren't interested). The married or in-a-relationship ones are interested in friendship, not an affair.