If Gmail is telling you that your storage is full, it means that you've used up all the available storage space in your Gmail account. Gmail provides users with a certain amount of free storage space, which includes not only your emails but also any attachments and files stored in Google Drive associated with your Gmail account.

Here are some steps you can take to address the issue:

Check Your Storage Usage:

Go to the Google One website (one.google.com) and sign in with your Google account.

On the left sidebar, you'll see "Storage." Click on it to see a breakdown of your storage usage.

Delete Unnecessary Emails:

Go through your Gmail inbox and delete any old or unnecessary emails, especially those with large attachments.

Empty your trash and spam folders as well, as these also count towards your storage usage.

For More Information Read: Why Gmail Storage is Full After Deleting Everything?

Use Automated Backup & Restore Tool

Corbett Gmail Backup Tool is one of the software available in the market that lets you backup & restore Gmail emails to the same or another account. With this software, one can easily download all emails from Gmail account to Computer with all properties. A demo edition of the software is available, which lets to evaluate the performance of Toolkit.