Jealousy itself is a secondary emotion. It's an emotion caused by another emotion.
Usually either envy - This person has something I wish I had, so I am jealous of them
Or fear - I have something, and I'm scared of it being taken away.
Or Anger - This thing is mine, how dare she expect me to share it.
You're not going to be able to deal with the jealousy without getting to the root of the primary emotion that's triggering it.
In your case, I'm guessing it's fear. You already have the thing (a relationship with your partner), so it's not going to be envy. And angry people tend to think their jealousy is justified, so it's unlikely to be that.
So the question is, what are you scared of? What is it about your partner talking to others is it that triggers you. Is it to do with worries about his faithfulness, your own self esteem, or something thats not right about the relationship itself.
Thats your starting point, and then start digging from there.