I have set the path of the attachment in the xml file. E.g. C:\Users\userX\Desktop\MailAttachment\Attachment.jpg
It works well if the attachment is in the directory.
However, if the attachment is not in place, the mail will not send out.
This is not a big problem but I would like to send the email no matter if the attachment is in place or not. I hope this feature can be added in the future. Thank you.