DKIM Failure for Emails with Content-Type: text/html

[DNCD]

Description:

Emails sent with Content-Type: text/html are failing DKIM checks, resulting in a "dkim=fail (body hash mismatch)" error. However, when emails are sent with Content-Type: text/plain, they pass DKIM checks without any issues.

Steps to Reproduce:

Send an email with `Content-Type: text/html`.
Check the DKIM status in the email headers.
Observe the "dkim=fail (body hash mismatch)" error.
Send an email with `Content-Type: text/plain`.
Check the DKIM status in the email headers.
Observe that the email passes DKIM checks.

Expected Behavior:

Emails sent with Content-Type: text/html should pass DKIM checks just like emails sent with Content-Type: text/plain.

Actual Behavior:

Emails with Content-Type: text/html fail DKIM checks with the error "dkim=fail (body hash mismatch)", whereas emails with Content-Type: text/plain pass DKIM checks.

does anyone know how to fix this?