We have a handful of external domains that, when we send meeting requests to recipients at these domains, we either do not receive any meeting accept message back or we do get the accept message but it is missing the message.ics embedded portion which seems to be required to update the meeting attendde's status. We have confirmed that the recipients are receiving the meeting requests and accepting them. Something seems to be blocking the accept responses and/or the message.ics portion of the email. I do not believe the blocking is on our side since it is only three domains we have this issue with. The recipient domains are also using Exchange. I've searched for days, no luck. Any insights?