Inbound mail queue not delivering to mailboxes Exchange 2016

All of a sudden, no mail being delivered. Mail steadilly building in the inbound queue. Internal mail OK. Sending external mail OK.

I can't see any reason for the queue not to deliver to the mailboxes.

Any suggestions
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snooflehammerAuthor Commented:
Update: I have the error 432 4.3.2 STOREDRV.Deliver ; dynamic mailbox database throttling limit exceeded

I can't find a resolution. No mail is being delivered to mailboxes
Sushil SonawaneCommented:
Check your server processer and RAM utilization control. Also check your event viewer if get any error message regarding exchange throttling limit exceeds.
snooflehammerAuthor Commented:
T runs out it was a failing drive array, even though the HP ACU did not show a degraded state.

Moved the edb file & logs to a new array and promblem fixed.
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Sushil SonawaneCommented:
still you are facing issue then share event log or run Exchange BPA see and troubleshoot accordingly.
snooflehammerAuthor Commented:
Found the issue myself & resolved
snooflehammerAuthor Commented:
Found a couple of referneces in the logs to long write times to the edb, so I moved it to another array

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snooflehammerAuthor Commented:
Founf the answer through my own research
For those of you that are facing the same issue and have confirmed it is not storage related, I had a client on 2016 CU2 for over 2 years with no problems.  Then all of a sudden, delayed emails everyday for weeks.  Turned out upgrading to .NET 4.7.1 and then Exchange 2016 CU10 resolved the issue with email delays.  I was pretty shocked.
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