You can use our Email to Record Importer for Airtable automation for this. This automation will generate a unique Email Address that you can then send/forward emails to. For any email received in this inbox, the automation will store the email's subject in the Subject Field, and the body in the Body Field.
Limitations
Formatting in emails may not be processed correctly.
The entire email body will be saved as one field, extremely long emails (e.g. with many replies) may run into field's limitations.