How to reduce OST file size

Dear Umarfarooque Momin,

Thank you for posting in Microsoft Community. It will be a pleasure working with you,

Managing large OST (Offline Storage Table) files in Outlook, especially in scenarios with limited storage capacity, can be challenging. Here are some suggestions to help reduce OST file size and manage storage more efficiently:

• Archiving Old Emails:
  • Encourage users to archive old emails that are not frequently accessed. Archiving moves emails to a separate PST file, which can be stored locally or on network drives. Ensure that users follow organizational policies regarding email retention.
• Compact OST File:
  • Outlook has a built-in compact feature that reduces the size of the OST file by eliminating unnecessary space. This process is automatic and usually runs when Outlook is idle. However, you can manually trigger it by going to File > Account Settings > Account Settings > Data Files > Settings > Advanced > Outlook Data File Settings > Compact Now.
• Clean Up Mailbox:
  • Regularly clean up the mailbox by deleting unnecessary emails, attachments, and items from the Deleted Items folder. This action helps reduce the size of the mailbox and subsequently the OST file.
• Limit Cached Exchange Mode:
  • While you've mentioned that reducing the timespan Outlook will make a cache is not allowed, consider whether any exceptions can be made for specific mailboxes that don't require a full year of caching.
• Adjust Mailbox Size Limits:
  • Check if there are any mailbox size limits imposed by the Exchange Server. If possible, increase these limits to allow for larger mailboxes. However, be mindful of server performance implications.
• Implement Mailbox Policies:
  • Implement mailbox management policies that automatically archive or delete emails based on specified criteria. This can be done through Exchange Server policies.
• Regular Maintenance:
  • Schedule regular maintenance tasks, such as compacting OST files and archiving, to keep mailbox sizes in check. Automate these processes whenever possible.

If none of these solutions work, please let me know and we can explore other options.

To notify us and have us get back to you, simply reply to this post.

Thank you,

Microsoft Community

Hello Umarfarooque Momin,

Good day!

Thank you for posting to the Microsoft Community. We are glad to assist. We are looking into your situation, and we will update the thread shortly.

Appreciate your patience and understanding and thank you for your time and cooperation.

Sincerely,

Eleni | Microsoft Community Moderator