How to export email archive as .mbox format
MBOX format is very common email archival format. This can be used to import mails to email clients like Apple Mail, Thunderbird etc. Here’s an article from Mozilla detailing the approach.
1) Go to the Migrate tab. Set the source as “Horcrux Backup”. Select the account and snapshot you want to export.
2) Set the destination as “Mbox File”.