I am still not able to send attachments. Upload works (verified in content path) with both upload options. Messages send successfully with no attachment. I’ve updated the code for MP_Pluggable_class.php as above, tried both with “MailPress version of wp_mail” and without. I used _sendmail and native php_mail. Both send messages successfully. After successfully uploading (many different file types), I always get (when following the attachment file link) “Cannot Open Attachment 1!”.
Are attachments only supported with SMTP?