I need some advice on exporting a very large Microsoft 365 Online Archive. The mailbox currently contains around 370 GB of archived email, and the requirement is to save the data as PST files organized by year. I started an export several days ago, but the Online Archive is still showing close to 370 GB, so I’m unsure whether I should continue waiting or try another approach.

I understand that large mailbox exports can take time, particularly when the archive contains years of messages and attachments. Outlook provides an Import/Export option when the Online Archive is available in the desktop application, but keeping Outlook available for such a long-running process is not ideal. There is also the possibility of export failures, and repeating a large export from the beginning could consume even more time.

I’ve been researching whether Export Online Archive to PST can be handled more efficiently by applying date-based filters. Since I need separate PST files for different years, filtering the mailbox before exporting seems more logical than producing one huge PST and trying to divide it afterward.

Microsoft Purview eDiscovery is another route I found. It can collect and export mailbox information, but the process requires appropriate permissions, compliance configuration, search setup, collection, review, and export. That seems more suitable when the mailbox data is being collected for compliance or investigation rather than simply creating a manageable archive.

For this type of large export, I also came across the SysInfo Microsoft 365 to PST Export Tool. The blog says it works without Outlook and supports Exchange Online, on-premises Exchange, and hybrid deployments. It can export Archive mailboxes and includes features such as date filtering, duplicate removal, skipping previously migrated items, splitting large PST files, and freeing server space.

The ability to apply filters is particularly relevant to my situation because I don’t want to repeatedly process the entire 370 GB archive. If each year's data can be selected separately, the resulting PST files should also be easier to manage and verify.

Has anyone successfully handled an Office 365 archive mailbox to pst export of several hundred gigabytes? I’d especially like to hear whether breaking the archive into yearly exports helped with processing time, PST size, and verification of emails and attachments.

Read More: https://www.sysinfotools.com/blog/export-online-archive-to-pst/