The mailing scripts that being authenticated with Gmail SMTP suddenly not function properly.
You will get below error message:
SMTP -> ERROR: Password not accepted from server: 535-5.7.1 Please log in with your web browser and then try again.
Learn more at 535 5.7.1 https://support.google.com/mail/bin/answer.py?answer=78754 ru4sm6912310pbc.25
SMTP Error: Could not authenticate.
Gmail phpmailer will prompt error like this normally when you changed the running script from one server to another. Even the Gmail account login credentials are correct, Google’s servers may still block the new server to authenticate.
To get this resolve, please log in using the same Gmail account in your browser, and then open the link below and go through the verification process:
This will authenticate a new server for your Gmail account. Kindly try to authenticating using the phpmailer again within 10 minutes.
You may also refer to https://support.google.com/mail/bin/answer.py?hl=en&answer=78754