shindy: there is a small pamphlet-like book that is probably sold in eichlers or a judaica/ torah treasures place….its called “Hee Tishallel (in hebrew) A Practical Guide to Tznius” by Rabbi Yaakov E. Forchheimer from Lakewood. he writes that “The men should speak to the men, and the women to the women. Although this woman may be your best friend’s wife, to you she is an eshes ish, and therefore an erva….The same is true for the women….By the same token, men and women who are not related should not call one another by their first names.” (page 37)Rabbi F. cites this from the Ibn HaEzer (Ibn Ezra), biShem the Maharshal.
hope this helped.
Thank you so much Bais Yaakov maydel. That is so true. Thanks for your pure words.