I do think men and women can be friends, but a married or family man striking up a new female friendship - the odd message or sharing a meme with a new friend wouldn’t bother me, but I wouldn’t like regular messaging, you know, sat at home in the evening together or a day out that’s being interrupted by a constant relay of messages between them, I’d find that a bit insensitive and would worry about a deeper connection forming. Meeting for drinks one to one outside of work sounds like a date. Group drinks would be fine.
Could be just my views but I wouldn’t like it and would feel like it’s over stepping boundaries.
i do also think that it’s important to realise that our discomfort with this could be partly due to insecurity, previous experience that proved unhealthy, or even the influence of general society/media telling us male and female friendships can never be platonic.
only you know your husbands personality - if he is acting out of character, seemingly excited about this friend, changing views or attitudes and this is making you uncomfortable or have doubts, I’d say that this is a relevant feeling and you’d be right to have concerns.
it’s a stereotype and not a rule, but I have found a lot of men in or approaching 40 plus seem to have some mid life crisis and enjoy way too eagerly and accepting of any ego stroking they can get. (Yes, same can be true for women I know). A lot of affairs have began through a harmless new friendship. A lot of harmless new friendships have remained just that. For me, if either of you are in a relationship, a friendship that becomes quickly intense with the opposite sex offers the potential to cross the line due to the emotional closeness that can develop and so boundaries should be in place.
ultimately, if someone is going to cheat, they will, you can’t stop them. You can speak calmly and openly to explain how you feel about a situation and hope they respect that. But I agree with others that laying down the law and telling him he cannot do such and such would possibly be detrimental and either cause an upset in your marriage or push the friendship along further