Older clients and Exchange 2016

Hello all,
I'm about to migrate our Exchange 2010 servers to 2016, but wondered about something. I read that versions of Outlook older than 2010 SP2 (with hotfix) can't connect to Exchange 2016 (see at the bottom of https://technet.microsoft.com/en-us/library/aa996719(v=exchg.160).aspx). Is this true only if the user's mailbox is hosted in an Exchange 2016 database, or even if the mailbox is stored in the old 2010 database?

In other words, can older clients, like Outlook 2010 (no SP installed) connect to a mailbox stored in Exchange 2010 through Exchange 2016?

Thank you so much for your answers!
SysUASystems AdministratorAsked:
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Pune TechCommented:
Exchange Server 2013 or 2016 continues to proxy the autodiscover request to Exchange Server 2010. Only you need to recycle the Autodiscover application pool on the 2016 server then the client will connect properly.

So older client outlook 2010 will be able to connect to exchange 2010 & 2016 servers without any issues.

Also refer following post

https://www.reddit.com/r/exchangeserver/comments/48b28n/outlook_2016_connectivity_issues_after_migration/
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AndyIt ConsultantCommented:
Hi,

As per the article, and as the clients will go via Exchange 2016 then, unfortunately, the only Supported clients are:
Outlook 2016
Outlook 2013
Outlook 2010 with KB2965295
Outlook for Mac for Office 365
Outlook for Mac 2011

So as long as you have KB2965295 installed (if you have WSUS just push it out if not already done!) then you should be fine.
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LesterClaytonCommented:
If Exchange 2016 becomes your CAS (Client Access Server), then you will no longer be able to access the mailbox, unless you are running Outlook 2010 with SP2 and KB2965295 or Outlook 2013/2016.  It doens't matter that mailboxes are on an older server - the Client Access Role is the important factor here.  Clients connect to the Client Access Server, and it in turn speaks to the mailbox databases. Clients don't talk to the mailbox database directly.
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SysUASystems AdministratorAuthor Commented:
Alright, after that last answer I went looking for a device with Outlook 2010 (SP1) and it was able to connect just fine after adding entries for mail and autodiscover to the hosts file pointing to the IP of the Exchange 2016 server. Which by the way is quite odd, given that MS states this old client shouldn't be able to connect at all. I will do some more testing though, but it's looking good.
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AndyIt ConsultantCommented:
I would be careful with that approach as you never know if/when it will not work.
It may work for now but it's much better and highly advisable to get the clients up to date otherwise you could find yourself in trouble after a future update.
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