To export an email in Canary on macOS,
1) From Canary, Open the email message > Click ‘More’ ( bottom right corner at the end of an email ) > Click ‘Show Original’ > Click Forward.
2) From Gmail, Open the email message > Click ‘More’ ( top right corner at the start of an email ) > Click ‘Show Original’ > Click ‘Download Original’. Send the downloaded message as an attachment.
3) From Apple mail, Open Apple Mail > Click on the email message download > Click on File > Click ‘Save As’ from the drop-down menu > Ensure the “Format” is set to Raw Message Source > Click ‘Save’. Send the downloaded message as an attachment.