E Mail routing through one of two exchange servers available


We are having an issue with email routing within our exchange environment which has us looking into ow email is being routed.

We have 2 Exchange 2013 servers which both have the MBX/CAS roles on them.  They use IIS ARR as a reverse proxy on them which was not fully setup for load balancing.

Issue: When one of the exchange servers is down/off all routing of email stops sending and connecting to mailboxes even on databases held on the second server stops.  No access to webmail.  When the server is up and running all mailflow /OWA access works perfectly.

We are trying to distinguish how and why mail is being routed through to the exchnage server which was switched off but no luck as of yet.  

Any advice would be greatly appreciated.  
Thanks in advance
Who is Participating?
Brandon MillerSystems AdministratorCommented:
I utilize a DNS round robin for our mail server as we have 3 of them running a DAG. It sounds like you may have a DNS issue. We have the same issue for about 30 second when one of our servers goes down sometimes its as little as 5 seconds but the next CAS/MBX server takes over the databases it goes away quickly.
MAS (MVE)EE Solution GuideCommented:
No comment has been added to this question in more than 21 days, so it is now classified as abandoned.

I have recommended this question be closed as follows:

Accept: Brandon Miller (https:#a42553552)

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