Are you somehow comparing volleyball to the partition between the men's and women's seating in a synagogue?

Outside the synagogue, the only rules on contact between genders are:

• Touching. You shouldn't touch someone of the opposite gender, other than your spouse or close relative. Many rabbis opine this is only with regards to "affectionate" touching (or touching that is very often affectionate); others say it precludes all touching (see the link regarding handshakes).
• You shouldn't be hanging around people of the opposite gender (again, other than your spouse) if they're dressed really inappropriately. Rabbi Moshe Feinstein recommended a five-foot tall, opaque mechitza in a synagogue, as it was likely that women would show up "with bared arms, and more"; put the average-height woman behind a five-foot wall, and usually all that's visible is her head (and even if she's not covering her hair, that's not considered "inappropriately dressed" today, according to Rabbi Feinstein).
• During the times of month that a married couple must be celibate, extra restrictions are added as a reminder for them; one spouse shouldn't throw things to the other.
• Beyond all else, reasonable sense should be applied regarding what sorts of behavior is likely to lead to inappropriate touching, looking, or thoughts. E.g. a married woman once asked Rabbi Mordechai Willig of Riverdale regarding going to the movies with her neighbor's husband (just the two of them, they're big Harry Potter fans). Without consulting with an official source or text, Rabbi Willig relied on his common sense to say that wasn't a good idea!

Especially with regards to that last point, different communities will have wildly different standards as to what's called "reasonable sense." (Or "we adopt blanket rules to avoid problems").

Are you somehow comparing volleyball to the partition between the men's and women's seating in a synagogue?

Outside the synagogue, the only rules on contact between genders are:

• Touching. You shouldn't touch someone of the opposite gender, other than your spouse or close relative. Many rabbis opine this is only with regards to "affectionate" touching (or touching that is very often affectionate); others say it precludes all touching (see the link regarding handshakes).
• You shouldn't be hanging around people of the opposite gender (again, other than your spouse) if they're dressed really inappropriately. Rabbi Moshe Feinstein recommended a five-foot tall, opaque mechitza in a synagogue, as it was likely that women would show up "with bared arms, and more"; put the average-height woman behind a five-foot wall, and usually all that's visible is her head (and even if she's not covering her hair, that's not considered "inappropriately dressed" today, according to Rabbi Feinstein).
• During the times of month that a married couple must be celibate, extra restrictions are added as a reminder for them; one spouse shouldn't throw things to the other.
• Beyond all else, reasonable sense should be applied regarding what sorts of behavior is likely to lead to inappropriate touching, looking, or thoughts. E.g. a married woman once asked Rabbi Mordechai Willig of Riverdale regarding going to the movies with her neighbor's husband (just the two of them, they're big Harry Potter fans). Without consulting with an official source or text, Rabbi Willig relied on his common sense to say that wasn't a good idea!

Especially with regards to that last point, different communities will have wildly different standards as to what's called "reasonable sense." (Or "we adopt blanket rules to avoid problems").