@pieter b we are also having the same problem and have been for over a month.
It's mostly with Microsoft email services and when I contacted support last week they said they already knew about it. They have put a "temporary mitigation" on our account over the weekend, but we don't know if it's made any real change yet.
@eric f11 please note that we went through the same thing with emails going to the spam/junk folder for people using Microsoft's email services a year ago with a different service. The problem is that Microsoft seems to pay a lot of attention to the sending email server's IP address to give it a reputation score. If the email server also sends bulk marketing emails it gets a poor reputation score and any other emails sent from that server usually end up in spam/junk. Our problem was resolved with the other service by them splitting their outgoing email servers by purpose. All marketing/bulk emails are sent from 1 group of servers and all regular emails from another separate group of email servers.
Also, we're very disappointed that Intercom knew of this problem but have left it up to us to find out ourselves. This affects anyone sending to outlook.com, hotmail.com, live.com, Office 365, Microsoft 365 and many business email accounts.