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mary_williams's avatar
mary_williams
Copper Contributor
Mar 17, 2026

Outlook Running Very Slow and Laggy

Hi everyone, I’ve been having issues with Microsoft Outlook running extremely slow lately. It takes a long time to open, switching between emails is laggy, and sometimes it even freezes for a few seconds.

I haven’t made any major changes to my system, but I do have a large mailbox and several folders, so I’m wondering if that could be the cause. I’ve tried restarting my computer and closing other apps, but the problem still continues.

Has anyone experienced this or knows what might be slowing it down? Any tips to improve performance would be really appreciated. Thanks

Mary

1 Reply

  • RobertSparnaaij's avatar
    RobertSparnaaij
    MVP
    Mar 18, 2026

    Your post doesn't contain enough information to troubleshoot performance issues.

    Are we talking about Outlook Classic here?

    What do you consider a large mailbox and folders in GB and number of items within the folders having the issue?

    Which mail account type are you using? Exchange Online, Exchange On-premises, Outlook.com, IMAP, POP3, other?

    If you are using an Exchange account, how do you have your Cache Mode settings configured?
    File-> Account Settings-> Account Settings...

    When you open Windows Task Manager, do you see a high CPU or Disk usage for the Microsoft Outlook process?

    Can you repro the issue in Outlook Safe Mode?
    Start-> type; outlook.exe /safe
    (note the space in the command above)

    Which COM Add-ins do you have installed and activated?
    File-> Options-> COM Add-ins

    Additionally see; Outlook doesn’t start, crashes or shows Not Responding | Robert 365