Send mails through scheduler event but last some mails get error

Hello,
I send mail in Welcome message on customer doctype mail-id using api and scheduler event through and i have many customer data which in message send successfully i check manually it is perfect and scheduler use that scheduler through some customer to mail send successfully but last some mail get error.

I will check in Email Queue in Generate Error like:
File “/home/frappe/frappe-bench/apps/frappe/frappe/email/doctype/email_queue/email_queue.py”, line 143, in send
ctx.smtp_server.session.sendmail(
File “/usr/lib/python3.10/smtplib.py”, line 902, in sendmail
(code, resp) = self.data(msg)
File “/usr/lib/python3.10/smtplib.py”, line 571, in data
raise SMTPDataError(code, repl)

I think, it’s an email issue, so again reset the email password and try it.

Hello @NCP I checked it’s not email issue it checked using manually send it is successfully send but when i scheduler set and scheduler send one by one automatic send in system that time this error generate.