Emails re downloading on outlook for mac

Debdeep Ghosh 0 Reputation points
2026-08-19T13:10:24.1466667+00:00

Hi

I have been using Outlook for Mac for the last 5–7 years. I have an active Microsoft 365 subscription, but my email account is configured as an IMAP account using my own domain email address.

My mailbox contains approximately 350 GB of email data.

The problem is that Outlook repeatedly starts re-downloading/synchronizing all my emails from the beginning. I have tried allowing Outlook to completely download and synchronize the entire mailbox. After the synchronization is completed, Outlook works normally for about 4–5 days, but then it starts downloading/synchronizing the entire mailbox again from the beginning.

This is becoming a major problem because of the size of my mailbox and the amount of time and bandwidth required for the repeated downloads.

I have already tried fully downloading the mailbox multiple times, but the issue keeps recurring.

Please help with the solution

Outlook | MacOS | Legacy Outlook for Mac | For home
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  1. Onyx Is here 4,770 Reputation points Independent Advisor
    2026-08-19T15:55:34.1233333+00:00

    Sorry to hear you're having trouble.

    As well as the information already provided I also had a suggestion. From your original post it sounds like you may have deleted the older emails (correct me if I'm wrong). If this is correct then it may be that for some reason the mails are possibly being saved on the website. I would suggest turning off synching on your app then log in on the website and delete any emails that are no longer required. Then do the same on your app. Restart the Mac before turning sync back on and see if the issue persists.

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  2. AI answer

    2026-08-19T13:10:46.61+00:00

    For an IMAP account in Outlook for Mac, repeated full re-sync behavior is commonly addressed by these supported actions:

    1. Reset the account cache in Outlook for Mac.
      • In Outlook, go to Tools > Accounts.
      • Select the affected IMAP account.
      • At the bottom, select Manage > Reset Account.
        This forces Outlook to re-sync the affected items.
    2. If the issue is specifically repeated folder content re-sync with Yahoo or AOL IMAP accounts, switch to New Outlook for Mac.
      • Open Outlook.
      • Turn on the New Outlook switch.
        Microsoft lists this as a workaround for Yahoo and AOL IMAP folder re-sync issues.
    3. If the account was added using Microsoft cloud sync, add the mailbox as a direct IMAP account instead.
      For IMAP accounts, the supported guidance in the referenced Q&A is to connect directly to the IMAP server rather than using Microsoft cloud sync.
    4. For Exchange accounts only, clearing the folder cache is another supported fix, but that does not apply to an IMAP mailbox like this one.

    Given the mailbox size of about 350 GB, repeated resets or re-syncs will trigger another full local download, so use Reset Account carefully because it will re-sync the account data again.

    References:

    AI-generated content may be incorrect. Read our transparency notes for more information.

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