https://www.stellarinfo.com/blog/how-to-export-exmailboxes-to-pst/

The following commands require a network share. Depending on server load, it might be best to use a share on another host.

New-MailboxExportRequest -Mailbox user@domain.tld -FilePath \\localhost\temp\user_company.pst

Get-MailboxExportRequest

New-MailboxImportRequest -Mailbox other.user@domain.tld -FilePath \\localhost\temp\user_company.pst -TargetRootFolder "Folder Name"

Get-MailboxImportRequest

Clear completed (or all) export requests:

Get-MailboxExportRequest -Status Completed | Remove-MailboxExportRequest

Get-MailboxExportRequest | Remove-MailboxExportRequest

Clear completed (or all) import requests:

Get-MailboxImportRequest -Status Completed | Remove-MailboxImportRequest

Get-MailboxImportRequest | Remove-MailboxImportRequest