All Outlook clients failing to connect to Exchange 2016

Exchange 2016 CU9 DAG 2 Nodes
Windows 2016 Data Center
Outlook 2013/2016

Today I woke up and all my Outlook clients are disconnected from my Exchange 2016 Servers.

Restarting the clients did not help

starting outlook in safe mode did not help either

I can access the accounts via OWA

Hope I can resolve this before everyone gets in today

What can I look for?

Any commands?

Thank you in advance
LVL 23
Thomas GrassiSystems AdministratorAsked:
Who is Participating?
I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

I guess you already checked database mount status.
Have checked whether you have any DNS issue?
Also outlook connectivity?
MASEE Solution Guide - Technical Dept HeadCommented:
Things to check
1. Ping which is configured in your Mapi virtual directory.
2. Ensure database is mounted
3. open outlook with /RPCDIAG switch and see what is the error.
4. Make sure you can reach server.
5. Finally Please recycle the mapi application pools or iisreset
6. If there is any change in app pools please revert back and recycle.

Hope it helps.

Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
Thomas GrassiSystems AdministratorAuthor Commented:

Thank you for your help

reverted back app pool change restarted IIS  now clients accessing
Thomas GrassiSystems AdministratorAuthor Commented:
REopen this

Clients not connecting again

Exchange 2016 is crap
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today

From novice to tech pro — start learning today.