How to backup gmail data before deleting email ID?
If you want to backup all the gmail data when an employee leaves the company before deleting his/her email address from the domain, follow the below steps.
1. Login to the desired email account from any browser.
2. Open a new tab and type the following address https://takeout.google.com/settings/takeout
This will take you to a page where you can see and manage all the applications from Google.
3. On this page we can select the content which we want to download like gmail, contacts calendars etc.
4. In our case, we normally download only gmail data once the employee leaves the company by selecting Mail as shown in the below picture.

5. Click Next and then Create archive to archive the data.

6. This will start creating an archive of the selected data.

7. Once the archive is ready, an email will be received on the same address with the link to download the data.
8. Click on the received link to download the data and store it in the Mail Backups Folder in the IT shared folder.
9. This will create a MBOX file.