Email Append To and Email Alert

i have an email account support@abc.come
i also add Append To ISSUE
so any one send an email to support@abc.com
the messages will delivered automatically to issue section ,

But the problem is:

i didn’t receive any notification when we got message on issue section ,

so i made an

Email Alart that track the issue status

and send an alert But it didnt work and get an error message

=================================================================
(504, ‘Invalid Username or Password’)
Traceback (most recent call last):
File “/home/frappe/frappe-bench/apps/frappe/frappe/email/queue.py”, line 306, in send_one
smtpserver.sess.sendmail(email.sender, email.recipient, encode(email.message))
File “/home/frappe/frappe-bench/apps/frappe/frappe/email/smtp.py”, line 174, in sess
(self.password or “”).encode(‘utf-8’))
File “/usr/lib/python2.7/smtplib.py”, line 622, in login
raise SMTPAuthenticationError(code, resp)
ValidationError: (504, ‘Invalid Username or Password’)

===============================================================

But when i change the Append To to for example todo
and goto issue section and make a new issue manually
i successful receive notification on my email

So what i noticed is a conflict between Append To and Email Alert

is there any suggestions ?