[Masahiko Kawai]

I have eliminated the need to enter my email address by doing the following

function bbp_set_default_email( $post_author_email ) {
	if ( empty( $post_author_email ) ) {
		$post_author_email = 'anonymous@example.com';
	}
	return $post_author_email;
}
add_filter( 'bbp_pre_anonymous_post_author_email', 'bbp_set_default_email', 10, 1 );

function bbp_remove_default_email( $r, $args ) {
	if ( $r['bbp_anonymous_email'] == 'anonymous@example.com' ) {
		$r['bbp_anonymous_email'] = '';
	}
	return $r;
}
add_filter( 'bbp_filter_anonymous_post_data', 'bbp_remove_default_email', 10, 2 );

First, use the filter hook “bbp_pre_anonymous_post_author_email” to set the default email address if the email address is blank.
This avoids the “Invalid email address.” error.

Second, if the return value “$r[‘bbp_anonymous_email’]” is set to the email address set earlier, return it blank.

This way, if an email address is entered, its value is returned, if it is blank, it is returned blank.