iPhones on Ios 11.x periodically stop syncing with exchange 2013 using activesync

I have multiple users that range from iPhone 5 through iPhone 8 that since upgrading to IOS 11.x have had intermittent problems and the fix has been to remove the account and put the account back on the device.
For some users this problem occurred once.
I also have 4 or 5 users that the problem happens multiple times per week.
There seems to be no rhyme or reason to the phone or ios level except that they are at least on IOS 11.

I am hoping someone can point me to some exchange logs and tell me what to look for to resolve this issue.  

It also seems that my exchange inetpub logs now are very large.  Maybe something in those logs will help with this resolution

We know there have been multiple problems with IOS 11.

Any info is appreciated.  et me know what additional information is needed
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Sunil ChauhanExpertise in Exchange Server, Office 365 & Powershell ScriptingCommented:
check the events logs on frontend servers, also check the logs on the Reverse proxy if its deployed.

to me it is sounding issue somewhere with the autodisover calls or active sync, try recycling the app pool for both on the front end for the same once.

also, you can enable active sync logging for further troubleshooting.

below article explains enabling and reading the logs in details.

EkuskowskiAuthor Commented:
A coworker just pointed out that the devices are actually able to send emails , they just cannot receive emails.
also Text messaging works during the problem and also web browsing.
The only problem noticed so far is receiving new emails does not work.
Just wanted to be clear on the issue
Tom CieslikIT EngineerCommented:
I went across this problem few days ago in my company.
After few hours of investigating I've decided delete his profile on iPhone and after restart, recreate it again.
So far so good. Hi did not reported any issue again.
EkuskowskiAuthor Commented:
I'm going to close the ticket and award points, We ended up engaging Microsoft support and I think our problem was more specific to our environment and individual users .  I do not have all the details of what Microsoft did to resolve the problem but this was the basics

      Default Naming Context
      under active sync container
      delete the  partnerships for the devices

After deleting the partnership for the affected user
delete the existing profile from the affected user device
reboot the device
create the new profile for the affected user.
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