Hello. My organisation has one forest containing two domains. The two domains correspond to two different geographical locations.
In the domain I manage, I have two Exchange 2013 CU5 Standard servers in a DAG. Both servers have both the CAS and Mailbox roles installed. The servers are running Server 2012 Standard. The two servers are on different subnets. One server, which is usually our active mailbox server, is at our primary data centre. The other server is at a standby data centre. The two sites are separated by a WAN link.
Our clients are at the primary data centre. They are on their own subnet. The clients run Outlook 2010 on Windows 7 Professional.
Exchange 2013 was deployed in my domain for about a year before the other domain began their deployment. During my deployment, the other domain had one Exchange 2007 server. They still have that server, as well as two Exchange 2013 CU7 servers in a DAG.
Several months ago, a few clients reported that they intermittently encountered delays of at least 30-90 seconds for the Global Address list to appear when they clicked on To or CC in a new e-mail message or an existing message they wanted to forward. This issue arose during the time at which the other domain was doing their Exchange 2013 deployment, but that may be a coincidence.
I have been able to determine that this issue usually happens the first time the user does this in their Outlook session. After that, the address list appears instantly. If Outlook is closed, and then restarted, the address list will again be slow to appear when the users attempt to use it.
Our organisation uses Outlook in online mode. I have tried Exchange cached mode, but that did not make any difference for me. Because an issue was previously encountered when cached mode was tried, management in my organisation is opposed to using it.
If you have any insights into the cause of this issue, and how to resolve it, please share them with me. Thanks.