Wordpress - wp_mail - Remove sitename from email subject
Finally, I wrote some code and it worked very well.
I hope it helps.
Put this in your functions.php
file
//remove sitename from email subject
add_filter('wp_mail', 'email_subject_remove_sitename');
function email_subject_remove_sitename($email) {
$blogname = wp_specialchars_decode(get_option('blogname'), ENT_QUOTES);
$email['subject'] = str_replace("[".$blogname."] - ", "", $email['subject']);
$email['subject'] = str_replace("[".$blogname."]", "", $email['subject']);
return $email;
}