Same event with my phone. I had the build released earlier in the week. Worked great for 24hrs, next day Email and Calendar won't open. Reset my Insider back to Fast, found the newest build, installed... everything else works fine. Outlook/Calendar both down. This morning, found this forum, went to App Store... keeps saying Outlook is installed. No option to update. Really don't want to uninstall and have to reconfigure all of my email accounts again. Will wait a little to see is there is a fix. Oh but the kicker is, Live Tile appears to work. Says I have 2 messages. ha...
Update 1: So I tried seeing if there was another update. No... Just for grins I toggled insider back to 3rd option... bam, found an OS update so pulling that down. Maybe I am behind and that could explain this. Will post results after update.
Update 2: on most recent build. no change. cal and outlook still broken