DANGER! DANGER! DANGER! Have you heard of EA's? (Emotional Affairs) That's often how people start out an affair, and many people who are in them do not consider them to be an "affair" because they are not physical....but they are one nonetheless, because the two people become emotionally invested in the other; it's more than friendship. This is also the precursor to a physical affair. And since my DANGER bells are ringing for you...just because he's says it's not physical...don't take that at face value.
Talking daily with this OW is unreasonable and unhealthy for your M...period, end of story. How did you find out he's talking daily with this woman to begin with? How is he going about doing this? In person, cell phone, office phone?
Hon...there's more going on here...and I'm not normally someone to jump to the "affair" conclusion.
This is a boundary that needs to be set in your M. Ask your H if he wants this M to work...if he does, then set the boundary...no more contact with this OW; you cannot move forward if you feel there is "competition". If he feels the need to talk to someone tell him to find a good male friend, talk to the C, or talk to you. He may use the reason that he talks to OW to get a woman's take on things...BS! Even if it did start out that way...he's drawing the OW in on an emotional level and chances are he's already involved emotionally too.
Please don't put blinders on to this, keep your eyes wide open! Just out of curiosity is this OW married that you know of? Has your H's behavior/schedule been different lately?
