Should a married man email a single woman all day?

If his wife doesn't know about it. The emails are just between two coworkers, he & I. They're from work & at home, but the emails are totally platonic. But, I begin to wonder, why is he emailing me so much when he is married. Shouldn't he be emailing his wife? Would you be mad if your husband was emailing a single woman if you didn't know about it, even if the emails were totally innocent? Thx.