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  1. Junior Member GLeung's Avatar
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    #1

    Default 2 questions regarding Exchange

    Is there a difference between RPC over HTTPs and OWA?

    Does cached exchange mode affect the performance of Outlook? I'm noticing Outlook opens faster when cached exchange mode is not checked off.

    Thanks.
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  3. New Member royal's Avatar
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    #2
    RPC over HTTPs is now known as Outlook Anywhere beginning in Exchange 2007. Essentially, RPC over HTTPs is used by Outlook and when Outlook first attempts to connect to Exchange, it tries to make MAPI RPC calls to what is defined as the Exchange Server in the Account Options. If the Exchange Server is not resolvable in DNS, Outlook will immediately fail over to utilize HTTPS functionality and then funnels those RPC calls through HTTPs packets. In addition to Outlook falling back to Outlook Anywhere if it cannot resolve the Exchange Server, it will also fall back to Outlook Anywhere if the Exchange Server specified in the profile is resolvable but does not respond after 30 seconds, it will also fall back to Outlook Anywhere.

    OWA is similar in the fashion that you connect to Exchange utilizing HTTPs but through a different client. In this circumstance, that client would be a web browser such as Internet Explorer, Firefox, etc... In OWA, everything is in Online Mode. Using Outlook Anywhere, if your profile is in cached mode, you will see cached data such as the Offline Address Book which updates every 24 hours (random time.)

    Cached mode definitely does change performance characteristics. In cached mode, Outlook client caches the mailbox data to an OST file. If you have a slow disk on the client, caching a large mailbox (> 10GB) can be detrimental to performance. There are registry keys that can limit the amount of data gets cached which affects both OST and PST files. If using a SSD on a client, it can handle >10GB mailboxes such as 20GB, etc... But this is obviously dependent on the performance of the SSD as well.

    Back in Exchange 2007 and prior, if using Online Mode across the board, it would increase the amount of IOPs on your storage that you would have to plan for. In Exchange 2010, Microsoft rewrote the store schema and changed the way the database was structured. It now put mailbox data together in a contiguous fashion and because of that, there is no longer a need to plan for additional IOPs due to clients using Online Mode. I wouldn't use Online Mode as a standard way to connect if you are centralized and have several branch offices as they will constantly utilize the private WAN circuits to pull data.

    Hope that helps.
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  4. Junior Member GLeung's Avatar
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    #3
    Thanks for the reply. So RPC over HTTPS could be used in this situation? A user has company issued laptop with his/her Outlook configured with his/her Exchange account. The user hits the road with his/her laptop which now takes it out of the company network. He/she can now connect to Exchange server?
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  5. Google Ninja jibbajabba's Avatar
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    #4
    Yes, but you'd need to configure Outlook Anywhere with a proper external domain and a SSL certificate which should be a SAN certificate (certificate with alternate names such as mail.domain.com and autodiscover.domain.com).


    You can test RPC over the Internet here:

    Microsoft Support Lifecycle
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  6. Google Ninja jibbajabba's Avatar
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    #5
    Sorry, wrong URL but I can't edit posts using the mobile skin here

    https://www.testexchangeconnectivity.com/
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