Responding to e-mail intros

When being introduced to someone, or multiple people, through an intro e-mail what is the most appropriate and professional way to respond? Assuming the introduction was offered over the phone within the context of networking for FT interviews.

I've seen some people address each recipient individually and then take it from there, but is this professional to do? Would it be more appropriate to respond individually and follow up later with whoever made the connection? Just curious what's worked well for other people, particularly when being introduced to two people in the same e-mail.