OP - my personal experience - XH was texting his mate's wife all day every day, as soon as he left the house. Thousands of texts over a couple of months. He started to talk about her all the time, he became infatuated with her. He walked out on me with no warning. I didn't discover the texts until after he left though. When I confronted him he denied it, despite the phone bills proving otherwise.
His best mates marriage has since broken up and XH and his female "friend" are basically living together, although they are telling people that she is just lodging in the spare room
.
She claimed that XH understood her like her own H didn't. XH claimed that they were just friends and she was supporting him because he was unhappy.
So sadly, in my experience, no, it is not right, can be very dangerous and in my case has led to the end of two marriages.
Your H appears to be open with you about the contact. That still doesn't make it ok though.