Outlook Mobile App - Can't Send to Private Contact List

_PRyan 

We are having the same problem with the Outlook mobile app on iOS and Android. The only difference is that while iOS won't send the email it at all (instead, it gives the message you mentioned), but Android sends it without any error message, but that immediately results in an NDR stating "Remote Server returned '550 5.4.103 ROUTING.NoConnectorForAddressType; unable to route for address type.'"

The problem is that everything worked just fine on both iOS and Android until July 23, 2021 (after about 2 years+ of use with private contact list groups). Suddenly, without any OS updates or App updates, the problem just appeared on 7/23. Everything continues to work just fine using webmail (even webmail through the web browsers on the mobiles) and on a PC, but it no longer works on either mobile OS. So far, no tech support with Outlook 365 has been able to figure out what the problem is (for us, anyway).

I noticed that mine seems to be the first and only reply to your post from February -- have you had any success at fixing this problem as of yet?