Hey all, Just so you don't tear your hair out like I did, it looks like Microsoft has a bad authoritative DNS server for subdomain ha.office365.com today which is interfering with autodiscover processes. cary@CaryBox:~$ host autodiscover.outlook.com autodiscover.outlook.com is an alias for autod.ha.office365.com. autod.ha.office365.com is an alias for autod.ms-acdc.office.com. Authoritative servers for ha.office365.com are: ha.office365.com. 3600 IN NS ns4-ms-acdc.office.com. ha.office365.com. 300 IN NS ns6-ms-acdc.office.com. ha.office365.com. 300 IN NS ns7-ms-acdc.office.com. ha.office365.com. 300 IN NS tm1.edgedns-tm.info. ha.office365.com. 300 IN NS ns5-ms-acdc.office.com. ha.office365.com. 3600 IN NS ns1-ms-acdc.office.com. ha.office365.com. 3600 IN NS ns2-ms-acdc.office.com. ha.office365.com. 3600 IN NS ns3-ms-acdc.office.com. All of these servers respond properly except tm1.edgedns-tm.info: cary@CaryBox:~$ dig +short cname autod.ha.office365.com @ ns5-ms-acdc.office.com autod.ms-acdc.office.com. cary@CaryBox:~$ dig +short cname autod.ha.office365.com @tm1.edgedns-tm.info cary@CaryBox:~$ Maybe it's just a problem with the local Ashburn resolvers? Just FYI in case anyone else is affected. Ticket open with Microsoft but it's going nowhere fast as per usual. - Cary