This article explains how to download your Gmail emails as a single mbox file, suitable for offline archiving or for uploading to an mbox-compatible email client.
How to Export AND Import a Backup of Your Gmail Emails
To download a copy of the messages in your Gmail account in the mbox file format:
To download specific messages, apply a label to those messages. For example, create a label titled messages to download and apply it to the messages you want to download.
Go to https://takeout.google.com/settings/takeout.
