Is my wife interested in another guy?

by Adam
(UK)

My wife and I rent out some property on our farm and recently my wife received a letter from a guy who used to stay on one of our cottages that we have on our farm a few years ago. I basically asked her how things were at our farm and how she was. He also gave my wife an e mail address and a recent pic of himself.

Sorting through my wife's e mail account I discovered that she had e mailed him back giving a bit of info on what had changed on our farm. She had also said "Good to see you!" when she had seen his picture, and she had finished the e mail with "do hope to hear from you again soon"

Is this a warning that my wife is possibly considering cheating? If it was an innocent e mail exchange why did she seem to express pleasure at seeing his pic? Should I talk to her about it, or let is pass? She would not be pleased if she knew I had been looking at her e mails.