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I have both on-prim exchange 2016 and 2019 DAG. once I moved a mailbox from exch2016 to 2019, the user cannot connect outlook. It ask username/password and but never works. Once I point server from loadbalancer directly to the exchange 2019 server, it works. It looks like exch2016 doesn't proxy connection to exchange 2019. I checked SCP, URL, they are all fine. What could be the issue?
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Hi @alan g,
Just checking in to see if below information was helpful. If you have any further updates on this issue, please feel free to post back. If you think my reply is helpful to you, please remember to mark it as an answer. Warm thanks.
It does proxy but if it fails at the load balancer, I would suspect the certs do not match between 2019 and 2016 or perhaps a TLS issue such as 1.2 not working through the load balancer perhaps.
The cert matches and same on 2016 and 2019. I don't think it is loadbalancer because I tested it by enter an entry using exchange 2016 server IP as the loadbalancer IP in host file, it still doesn't work. This bypassed the load balancer. The exch2016 server should proxy to 2019 server directly.
Regarding TLS, does 2016 and 2019 use different version and not compatible?
Yea you should verify its enabled for TLS 1.2 on both ( 1.3 is avail for enabling as well)
what is default TLS version exchange 2019 use? Isit not compatible with Exch 2016? I installed it using default setting.
1.2 is the default in 2019 now but I would still verify its enabled for 2016 and 2019.
TLS1.2 is enabled. I also disabled TLS1.3. This still doesn't work