Issue with mail app on ios with an Exchange 2010 account Cannot get mail The connexion to the server failed

Did you check the Event log? filter the events for activesync logs.

Have you tried Outlook for iOS app?

HI, nothing relevant in the "Application" log on Exchange....

Yes, It works with the Outlook app but it doesn't fix the original problem and the user want to keep the mail app of Ios.
And antother user had the same problem 2 weeks ago, he use the outlook app AND the mail app and each app failed to sync..

Have you tried to restart IIS using the IISReset command-line utility?

Yes I did it. No success ...

Updated to iOS 11?

If yes, it is a known issue.

https://www.reddit.com/r/apple/comments/714cqa/ios_11_exchange_email_warning/

That is probably it...really ridiculous issue. Apple with no warning decided to release a flawed release and we IT grunts get the blame for it...
This is a suggested workaround to do on the Exchange side but I haven't tested it yet...
https://tecadmin.net/enable-tls-on-windows-server-and-iis/#

suggested here:
https://forums.developer.apple.com/thread/79446

Google did similar thing also when Android 6 was launched.

https://forums.androidcentral.com/samsung-galaxy-s6/664555-exchange-email-not-syncing-after-marsmallow-update.html

What really irks me is this may not be a bug but a *feature*.
There is some discussion that the root cause of this is that iOS11 no longer supports the TLS1.0 protocol for security authentication. This must have been a deliberate decision by Apple. It has been a known issue since early beta.
https://github.com/AFNetworking/AFNetworking/issues/3999

That is why the 'fix' suggests enabling TLS1.2

This also affected an internal web server here and we had to upgrade it to support TLS1.2

The intention is good to upgrade security but they should have given some warning about it first. There is ZERO communication from Apple they would be discontinuing support for that protocol.

It is not a bug but a collaborative decision between Microsoft and Apple. Microsoft is a shareholder of Apple and should be knowing what Apple is doing for iOS 11.

Microsoft is pushing customers to "upgrade" from on-premises Exchange server to Office 365 Exchange Online and has no contractual relationship with most customers of on-premises Exchange servers as most of them will not buy a support service from Microsoft. Besides, Microsoft will only suggest users to use Outlook for iOS and do make warning that there will be issues for different versions of activesync from different versions of Exchange server when third party apps are used (including the native mail client of iOS and Android OS).

Thanks, that makes sense. So, in short, it's a scumbag move from both Microsoft and Apple :).

I test the account on an iphone not upgraded and same result, adding the account is ok the sync stops at the same date....

Did you remove all mobile devices listed under the user before you add the exchange account in iPhone?

Yes I did remove all partnerships before I configure the account on the iphone.

In such situation, troubleshooting shall be on whether it is a user or device related problem.

If you add exchange account of the user in another iPhone, is it the same problem? If yes, it is a user problem and if only one user has a problem, it is related to the mailbox issue and you need to do a mailbox migration or you need to do a manual check in ActiveSync log to see which entry in the user's mailbox has caused the stop of the sync.

If no, it is a device problem and you shall factory reset the iPhone 6.

I configure the same account on my iphone Mail app : same result fail
I configure the same account on my iphone Outlook app : it works
Another user had this problem 2 weeks ago, the problem resolves "by himself" few hours later ...
What a mess ...

Then, it is related to the mailbox of the user and it is time-consuming to troubleshoot.

How large is the mailbox of the user? Have you tried to do the initial sync over wifi or 3G?

The problem is Microsoft will not help you to support a third party email client and Apple cannot help you to troubleshoot an Exchange email account.

I just did a test, move an element that fails from sync from inbox to the sending box, I see it, sync is ok....So this is a problem related to the inbox ...about 12Go 30.000 element but only sync 1 month

Yes. I think you can solve the problem eventually but it will somehow happen again.

Any update?

No more update, no bugs since the last one. Just have to explain to my users that computing is not an exact science ... once again ! And they will think that I'm just no good ... Once again !

Clip some news on iOS 11 and advise your users to switch to Outlook for iOS.

It is the expected outcome for an Apple and Microsoft "cooperation".

Update on the 'cooperation'.
iOS 11.1 beta did fix the email issues for most if not all on-prem users.
Not sure when this will go to public release..maybe when iPhoneX is released.

Thank youSeeDk even if it does not concern my problem finally.

That was the only solution to make the original iOS mail app working again.