Exchange 2013 CU5 on Server 2012 R2 fresh install/new to domain; Outlook 2010 or 2013 on Remote Desktop server not in cached mode is slow to open, search and send messages with attachments. Opening messages and opening attachments runs quickly.
My test mailbox has 300kb worth of mail in it and sending a message with a 5Mb attachment locks up Outlook for close to 1 minute and takes another 30 to 90 seconds to disappear from the outbox and and move to sent items. This issue does not present itself in OWA. My current testing RDS environment is a fresh install of Server 2008 R2 with Outlook 2013. No additional add-ins or AV running on the Exchange server or the test RDS server.
When cached mode is enabled, Outlook runs better as shown in Outlook 2010 (+ Exchange 2013) works extremely slow; however, I don't consider this an option because there isn't enough drive space on the RDS server to cache all of the user profiles.
Other Exchange environments - Outlook 2010 or 2013 in an RDS environment (non-cached) with Exchange 2007 or 2010 - don't show the same performance issues. Moving within Outlook and sending large attachments runs quickly.
I have checked Exchange throttling settings and monitored logs, but have not found cases where my test user is being throttled. I have also looked at turning off IPv6 based on another post's suggestion; however, I have seen conflicting information about disabling IPv6 for Server 2012 R2, so I have not yet gone down this path.
The Exchange server is a VM on a new VMware host and has assigned 8 cores from Intel Xeon E5-2640 procs and 16GB RAM; 1TB thick provisioned database volume on a RAID 5 array with 6 x 10k RPM SAS drives. Disk queues are low on the Exchange server (in the .20 to .70 range). My test RDS server is on the same VMware host on the same vSwitch. Another test system is on a different system, but exhibiting the same behavior.