Please note that you can not reply to a personal message by replying to the notification email.
Recently admins have received some email responses to personal messages. This is because some members have replied to the notification email. You can not reply to a personal message via the email.
What replying to the notification email does is send a copy of the original message and the reply to the admin email address. It does not send your reply to the person who sent you the message.
The email notification of the personal message does request "PLEASE DO NOT REPLY DIRECTLY TO THIS EMAIL!"