I have been looking for a practical way to save a large IMAP mailbox before moving to another email platform. The mailbox contains years of correspondence, attachments, and several custom folders, so I’m more concerned about preserving the organization than simply downloading the messages.

One option I’m considering is to export IMAP to PST, especially because PST is convenient for users who already work with Outlook. However, I would want the exported file to retain the original folder hierarchy, timestamps, attachments, and message information. Manually downloading thousands of emails doesn't seem like a realistic approach for a large mailbox.

Another concern is duplicate data. If a mailbox has already been backed up once and another backup is required later, repeatedly exporting the same messages could create unnecessary copies. An incremental approach that can recognize previously processed items would make subsequent runs much easier to manage.

While comparing solutions, I came across the SysInfo IMAP Backup Tool. The features that stood out to me were folder mapping, mailbox preview, date-based filtering, duplicate removal, and the option to process multiple accounts through CSV-based authentication. It also supports saving IMAP data into several formats instead of limiting the output to one option.

I also like the idea of being able to select specific emails instead of transferring an entire mailbox. For example, an administrator may only need messages from a particular date range or correspondence involving certain senders or recipients.

For organizations, an IMAP email backup can be useful before an account is deactivated, a provider is changed, or a larger migration begins. Keeping a local copy can also make it easier to access historical correspondence when the original account is no longer available.

I’m curious how others approach this. Do you normally create a complete mailbox backup before migration, or do you filter the data first? And if you use PST as the output, how do you make sure the folder structure and attachments remain intact?