Store Less Mail Locally With Thunderbird for IMAP

Choose to keep only the most recent emails on your computer

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How many copies of every email in every folder do you need? It's good to have them all on the IMAP email server, of course, in backup copies at the email service, and locally in an email program. However, it might not be necessary for Mozilla Thunderbird to download all your new mail whenever you start it and to store gigabytes of old mail, too.

Whether you use Mozilla Thunderbird only sporadically or want to preserve disk space on a mobile machine, you can set it up to store only the most recent messages on your computer.

Instructions in this article apply to Mozilla Thunderbird 68.4.2 or higher on Windows 10, 8, or 7, Mac OS X 10.9 or higher, and GNU/LINUX.

Leave Last Year's Emails on the Server

Set up Mozilla Thunderbird to keep only a certain amount of mail locally for fast search in an IMAP account. What counts as recent is mostly up to you.

  1. Start Mozilla Thunderbird.

  2. Select the Menu icon in the upper-right corner of the Mail window and select Options.

    Screenshot of Options in Thunderbird menu
  3. Select Account Settings in the Options menu.

    Screenshot of Account Settings in Thunderbird Options menu
  4. Select Synchronization & Storage in the left pane of the Account Settings window.

    If you have multiple accounts set up in Thunderbird, make sure you select the Synchronization & Storage category for the account you want to change.

    Screenshot of Synchronization & Storage in Account Settings
  5. Select Synchronize the most recent under Disk Space.

    Screenshot of Synchronize the most recent under Disk Space
  6. Choose the time for which you want Mozilla Thunderbird to keep a local copy of your emails. Select 6 Months, for example, to have six months of email available offline for quicker searching capabilities.

    You can choose Days, Weeks, Months or Years in the Synchronize the most recent drop-down list.

    Screenshot of Synchronize the most recent options
  7. Select OK to apply the changes, close the Account Settings window, and return to the main screen in Thunderbird Mail.

Search All Mail in Thunderbird

Older messages still appear in the IMAP account's folders. It is just the message text that is not kept on your computer for faster access. If you delete such an older message, it is removed from the IMAP server, as well.

You can search all mail, including mail only available in full on the server.

  1. Start Thunderbird.

  2. Select the Menu icon in the upper-right corner of the Mail window and select Find.

    Screenshot of Find in Thunderbird menu
  3. Select Search Messages to open the Search Messages window.

    Screenshot of Search Messages in Find menu
  4. Select the Run search on server checkbox.

    Screenshot of Search Messages window
  5. Select the search parameters you want to use, such as Subject contains and any words you want to search for, then choose Search.