2016 should automatically proxy to 2010. The endpoint from the perspective of the device is the 2016 server, so that should indeed be what is reflected in the device configuration.
I would wonder about how you have the EAS vDirs configured, both for URLs and authentication. From: listsad...@lists.myitforum.com [mailto:listsad...@lists.myitforum.com] On Behalf Of Kennedy, Jim Sent: Wednesday, June 28, 2017 2:37 PM To: exchange@lists.myitforum.com Subject: [Exchange] RE: 2010-2016 coexistence for ActiveSync I should add, a mailbox on the 2016 server with the temp.domain.com set up works just fine. From: listsad...@lists.myitforum.com<mailto:listsad...@lists.myitforum.com> [mailto:listsad...@lists.myitforum.com] On Behalf Of Kennedy, Jim Sent: Wednesday, June 28, 2017 2:20 PM To: exchange@lists.myitforum.com<mailto:exchange@lists.myitforum.com> Subject: [Exchange] 2010-2016 coexistence for ActiveSync Pre upgrade environment. 1 2010 CAS cas.domain.com 2 2010 MBX Current environment. 1 2010 CAS 2 2010 MBX 1 2016 Exch box temp.domain.com So, the next step is to get the 2016 box to act as the CAS for the mailboxes on the 2 2010 MBX boxes for OWA and ActiveSync. Got OWA no problem. ActiveSync for Android/iPhone is not co-operating. Looking at the above, what I am trying is to just manually edit the account info on the phone show the server is temp.domain.com Windows Auth for Microsoft-Server-ActiveSync on the 2010 CAS.
