Hi Marco, I had issue connecting Outlook 2016 on Windows 10 through external with autodiscover. Same profile i can setup Outlook 2010 no problems, but always got an error message during profile creation with Outlook 2016. (clean install on windows 10). Successfully passed autodiscover step but sign in to server failed with error "Cannot connect exchange, server must be online.."

I connected successfully after I changed the value from null to true..

hmm strange.

For the setups i did for Exchange 2016 they could always connect externally.

Not to say that command shouldn't be set though, as i do think its best practice to set in on mailbox, just surprising it doesn't work for you without it.

anyways, i will report back when i made a fix for that. normally it shouldn't take too much time.