Exchange 2010 SP3 rollup 8v2: three CAS/HT servers with load balanced VIP of mail.domain.com. That domain is used for all internal and external URLs except autodiscover sets the server value in Outlook to outlook.domain.com when using OA. This has and continues to work perfectly for Exchange 2010 mailboxes. These servers are running on Server 2008 Ent. All servers are virtual with 64GB ram and multiple 10G NICS iSCSI MPIO, Mapi, and Replication.
Exchange 2013 SP1 CU8: four multirole servers with a separate load balanced VIP of mail.domain.com (same as 2010). That domain is used for all internal and external URLs just as it is in the 2010 servers. These servers are running on virtualized Server 2012 R2 with the same config as the 2010 servers.
The OutlookProvider values for EXCH, EPR, and WEB are set to msstd:mail.domain.com
When I changed DNS to point mail.domain.com and autodiscover.domain.com to the Exchange 2013 VIP I received a number of complaints from end users that they either could not connect to their 2010 mailboxes or the connections would drop and not reconnect for extended periods of time.
I backed the DNS changes out and am now testing using virtual desktops with host file entries for both mail.domain.com and autodiscover.domain.com to the 2013 servers. What I've found is:
- A mailbox on the 2013 system will connect perfectly and immediately using Outlook or OWA and is rock solid.
- A mailbox on the 2010 system will sometimes connect and disconnect when using Outlook but works perfectly in OWA.
I've seen other questions about similar issues but have not found a solution that helps. Any thoughts are appreciated.