There is a bug with Lightroom and outlook from office 2016 that is still unresolved as far as I know: Lightroom : Email Photo doesn't offer Outlook 2016 as option? I think it is not getting fixed since so few people use this feature aNd even fewer use outlook as their mail client on Mac OS X since the built-in mail app connects to exchange servers.
It might be a good idea to post a bug report on this on http://feedback.photoshop.com. I couldn't find one there yet.
your reply doesn't help either. Only entourage is the possibility.
Have also tried through email account manager, settings:
smtp server: smtp.office365.com
connection security: STARTTLS
authentication method: no authentication.
The validation went ok but still cannot send e-mails.
I will re-install office 2011. Regret to have purchased this office 2016.