Exchange Event 4002


I was reviewing some event logs this morning for our Exchange environment. Upon doing so, I noticed that our Mailbox servers were constantly recording an event 4002, MSExchange Availability error in the event log. (screenshot attached)

Our Exchange environment is 4 CAS servers (one is from our old environment, where the public folder databases still are) and 2 Mailbox servers. (DAG) The errors are being recorded in the event logs for the mailbox servers.

I was reading the following article, regarding availability. I went ahead and checked where the external and internal url's were pointing to for the Web Services Virtual Directory and they had the same URL. (same url that was in the error log)

That article mentioned that the DNS for mail.<domain name>.com and autodiscover.<domain name>.com need to be pointed toward an array member, which isn't the case for us. record is pointed to our primary CAS  server IP, which is a member of the array. is pointed to our old CAS server (which is running SP1, other CAS are on SP3)

Could this possibly be the issue here? Any support on this matter would be greatly appreciated.

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AmitIT ArchitectCommented:
Can you share your AD Site design? As requests are going to another site or cross-site.
victory2201Author Commented:
If you are referring to the way our AD communicates between each physical site, then cross-site would be us.
AmitIT ArchitectCommented:
Let me ask me this way:

All Exchange are in one site or they are spread across other sites?
victory2201Author Commented:
Ok, thanks for clarification.

Entire Exchange environment is located at the same site.
AmitIT ArchitectCommented:
Where is the old CAS, as it is trying to connect to exchange in different Site.

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