WordPress at a glance
filter is not described

woocommerce_mail_content filter-hook . WC 1.0

wrap the content with the email template and then add styles.

Usage

add_filter( 'woocommerce_mail_content', 'filter_function_name_488' );
function filter_function_name_488( $style_inline ){
	// filter...

	return $style_inline;
}
$style_inline
-

Where the hook is called

WC_Admin::preview_emails()
woocommerce_mail_content
WC_Email::send()
woocommerce_mail_content
woocommerce/includes/admin/class-wc-admin.php 201
$message = apply_filters( 'woocommerce_mail_content', $email->style_inline( $mailer->wrap_message( $email_heading, $message ) ) );
woocommerce/includes/emails/class-wc-email.php 650
$message              = apply_filters( 'woocommerce_mail_content', $this->style_inline( $message ) );

Where in WP core the hook is used WooCommerce

Usage not found.