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Outlook cached mode is slow receiving email from on prem Exchange

Ben Lan 181 Reputation points
2021-01-23T00:12:57.06+00:00

We have Exchange 2016 on premise server w/ about 150 clients. All are configured to connect their Outlook 2016 client using online mode. Many users are experiencing performance issues such as lagging when access folders and also getting Outlook not responding errors.

My thoughts were to force everyone one to use Outlook in cached mode, especially since most of our mailboxes are less than 10gb. Our archiving solution allows us to keep our mailbox sizes tamed.

So we started deploying converting some users to use cached mode but noticed that this causes a delay in receiving emails from the Exchange server, The delay can be any where from a few seconds to a minute.

This may not seem like a long time but actually is when you are on the phone with a client who is sending you multiple emails and you have these delays for each one it can seem like an eternity.

Is there any configuration other than what is in the cached mode settings that can be the cause of such delays?

Outlook Management
Outlook Management
Outlook: A family of Microsoft email and calendar products.Management: The act or process of organizing, handling, directing or controlling something.
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Exchange Server Management
Exchange Server Management
Exchange Server: A family of Microsoft client/server messaging and collaboration software.Management: The act or process of organizing, handling, directing or controlling something.
7,503 questions

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  1. Andy David - MVP 145.6K Reputation points MVP
    2021-01-23T12:50:45.423+00:00

    That actually sounds normal. In real time I can see how it may seem like an eternity.
    If a user is on the phone with a customer and expecting emails in real time, can they use OWA instead? That should work quicker in that regard.

    I would continue using cached mode however for Outlook, that's really a best practice and how the architecture is designed to run optimally.

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  2. Yuki Sun-MSFT 41,016 Reputation points
    2021-01-26T05:37:30.547+00:00

    Hi @Ben Lan ,

    The delay can be any where from a few seconds to a minute.

    As mentioned by Andy, the slight delay seems to be a normal behavior in cached mode.

    Given this, aside from switching to OWA, you may also try clicking the "Update Folder" button on the Send/Receive ribbon to force a sync of the Exchange account when you are on the phone and waiting for a mail:
    60480-1.png

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  3. Ben Lan 181 Reputation points
    2021-01-29T19:42:19.097+00:00

    So I thought about approaching this a differently. I know our users will complain about the delays, they are non-technical and just don't get it. But what if I able to delay the incoming mail by a few seconds, thus givng the cache-mode a chance to receive the email and make it appear to come in the same time as it does on their mobile or OWA.

    Just a thought.