Issues with Office 365/Outlook ID 26

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This topic contains 5 replies, has 5 voices, and was last updated by Avatar Abul 3 years, 8 months ago.

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    Hi everyone hoping I am in the good subforum, here is my situation

    I have 6 clients (offices) for about 300 PCs and all of them has the issue, we keep getting a random time, an event ID 26 in event viewer that says Connection to Microsoft Exchange has been lost, Outlook will restore the connection when possible.

    This issue happens randomly, and not all users will get the error at the same time (some of them might get it like 3 times per day others like 20+)

    All of my client are using Juniper SRX firewall, and as of a test I even made a temporary policy that lets 100% of the ports out on the internet unfiltered for 100% of the PC and the issue happens again.

    I tried connecting one of my client email address to my personal PC and the problem does appear (rarely but still appear) my personal router is a TPlink.

    All the PC uses a combo of Windows7/10 + Office 2007-2016 and any combo has the issue.

    Stuff I tried
    -Changing the MTU
    -Removing the sleep on the NIC
    -Doing a ping script to (When I get the error, the ping still works)
    -Changing the default timeout on outlook
    -Removing the ‘Cached mode’ of Outlook
    -Réinstalling Outlook
    -Disabling IPV6

    I’m getting out of options atm

    Thanks if anyone can help


    Since it is Office 365, have you checked the Admin Centre for service issues, and have you raised a case with Microsoft?


    Raising a case with Microsoft was my next step (as for service issue there is none)

    I just wanted to check with others before raising a case

    also this issue seems to have been existing for a bit, but we didn’t notice before Windows 10 (Windows 7 users doesn’t seem to get the pop up but the ID pops)


    If it helps any we see it as well.

    Doesn’t bother us as cached mode is turned on.

    What do you mean (Windows 7 users doesn’t seem to get the pop up but the ID pops)


    How are you connecting to your server (HTTP / HTTPS)?


    If it is Office 365, it must be HTTPS

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