I need to reduce OST file in my outlook,

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I need to reduce OST file in my outlook,

Olorunfemi Adeleke 0

I need to delete files in my Outlook,it is IMAP, but it has exceeded the size

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2 answers

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Answer 1

Hi!

You can empty the Deleted Items folders, archive old emails, and delete large attachments to reduce file size.

The OST file is just an offline cache file, so you can delete it as well if you prefer.

For compacting, see the Q&A Assist answer or the article below:

https://support.microsoft.com/en-us/office/reduce-the-size-of-your-mailbox-and-outlook-data-files-pst-and-ost-e4c6a4f1-d39c-47dc-a4fa-abe96dc8c7ef

To delete the OST file, close Outlook > press Windows + R > Type %localappdata%\Microsoft\Outlook > Delete the OST file named after your email. When you delete an OST file, open Outlook and a new OST file will be created.

If you want to keep this OST file, you can simply rename it to any name, such as your_email_backup.ost.

Answer 2

AI answer

To reduce the size of the OST and get back under the limit, use a combination of cleaning up mailbox content and compacting the data file.

Clean up mailbox items (reduces what must be stored in the OST)

Because the account is IMAP, the OST is a local synchronized copy of what is on the server. To shrink it, delete or move items so there is less data to sync.

a) Use Mailbox Cleanup

In Outlook, select the File tab.
Select Tools > Mailbox Cleanup.
Use these options:
- View Mailbox Size to see which folders are largest.
- Find items older than a certain number of days and delete or move them.
- Find items larger than a size (for example, 5000 KB / 5 MB) and delete or move large messages.
- View Deleted Items Size and then Empty Deleted Items folder.
- View Conflicts Size and Empty Conflicts if available.

b) Search for large messages

Go to the IMAP mailbox in Outlook.
Click in the Search box and type: messagesize:>5 mb
Delete unneeded large messages or move them to a separate Outlook Data File (.pst) if needed.

c) Empty Deleted Items After deleting messages, make sure the Deleted Items (or Trash) folder is emptied so the space can be reclaimed.

Compact the OST file (actually shrinks the file on disk)

After cleaning up items, compact the OST so its physical size is reduced.

In Outlook, delete items you do not need and empty the Deleted Items folder.
Select File > Account Settings > Account Settings.
On the Data Files tab, select the IMAP data file (the .ost file), then select Settings.
Go to the Advanced tab and select Outlook Data File Settings.
In the Outlook Data File dialog, select Compact Now, then select OK.

Outlook also compacts automatically in the background when there is more than 20% unused space in the file and Outlook is idle, but running Compact Now forces it immediately.

If the OST is hitting configured size limits

If the OST is approaching a configured size limit (for example, via registry-based limits like WarnFileSize or WarnLargeFileSize), Outlook may:

Block sending or moving items.
Trigger Mailbox Cleanup.

In that case, continue to delete or archive items from the mailbox (as above) so the OST can compact below the warning threshold.

Be careful if editing any registry-based size limits; incorrect registry changes can cause serious problems. Always back up the registry first and only change these settings if fully familiar with the documented procedure.

References:

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I need to reduce OST file in my outlook,

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