Hi, our client has one Exchange 2010 Standard server. We have successfully installed Exchange 2016 standard in the domain and now we are preparing to do a cutover of DNS records from 2010 to 2016. After that we will migrate mailboxes and eventually decommission the old 2010 server.
I have a question and I think it has to do with the fact that we did not perform the cutover yet. Everything and everyone is right now still connecting to the 2010 server at this point. All DNS records point to 2010 (internally and externally) We will be using the same name webmail.company.com with certificate etc. All Virtual Directorys have also been named the right way.
It seems that Exchange 2016 can proxy stuff back towards Exchange 2010 (webmail for example) also there is mailflow between the 2 servers with a test mailbox.
If user A (2010 mailbox) logs on to EX2016\OWA he ends up in 2010 OWA, all good.
if user B (2016 mailbox) logs on to EX2016\OWA he ends up in 2016 OWA, all good.
if user B (2016 mailbox) logs on to EX2010\OWA he gets an IIS error
I believe this has to do with the fact that Exchange 2010 cannot forward everything towards 2016, but 2016 can do it towards 2010 ( After cutover )
Also at this moment we can setup an iPad and (externally) connect to user A (2010 mailbox) If we want to setup user B (2016 mailbox) account cannot be verified. I believe this also has to do with the fact that we have not done a cutover. Exchange 2010 cannot forward this credential / mailbox lookup to 2016?
Is this normal behavior? I would like to know before moving on to the next step. It makes sense to me that this is happening but I will have to plan the cutover with the 100+ users...