I don't think jealousy necessarily has anything to do with any mental illness/state; some people have that attribute/training/background is all. I'm with you Pucca and neither I nor my husband would have trouble going out alone with someone of the opposite sex and/or telling the other; my husband recently asked me to befriend an old girlfriend who had contacted him on Facebook because she was having problems and he didn't know how to deal with them and thought I'd be better at helping her! I did contact her (even recommended she come here) and now we email occasionally, having had a good several emails and she's my friend on Facebook too. He has several old girlfriends who have contacted him on Facebook. I actually told the one I mentioned "thank you" as I figure it is she and the other women who have been in his life (his first wife, especially) who "trained" him so well so he's an excellent husband now, LOL. I got the benefit of their rubbing off some of his rougher spots and polishing him up

Were I you, I would tell your husband you're going to lunch with a guy friend you knew in high school and do it in such a way that you sound excited/pleased and expect him to fall in with your mood. If he expresses anger or jealousy, express "calm" surprise in return? Ask if he'd like to meet him before/after or suggest maybe you all have a party and invite he and his wife and some other couple friends or whatever but explain to him, calmly, that his feelings about your friend whom he does not know (yet) don't count for a whole lot; that presumably he knows and trusts you or he wouldn't be married to you and his "ugly" words/thoughts are uncalled for and you find them hurtful.