The sad truth is that if one of the partners in a marriage is unhappy and is looking for an out, that's when the potential problems start - texting, instant messaging, emailing, phone calls, whatever, is only a symptom and the other partner cracking down on it will only exacerbate the situation. I'm not in any way condoning infidelity or the steps that lead up to it, but perhaps a more frank conversation about where they each are in the marriage is called for. If it turns out to be nothing, at least words that can't be taken back will not have been exchanged.