How to view Export Mailbox status in Mail App? How to view Export Mailbox status in Mail App?

I am trying to archive my mails: I created a Smart Mailbox, which includes the mails received in last year, then right click Export Mailbox to a .mbox file.

In the User Interface of Mail App, no export progress/ status is being displayed. How can I view the export status?

I can now only guess the export status is complete or not by checking the .mbox filename contains .partial or not.
Window > Activity - will show you what the mail app is busy with 

i.e. Exporting mailbox, copying 2551 of 3762 messages and a progress bar