SMTP Mails Blocked

[RajKumarSHhelp]

We are facing the email issue under one domain and we are trying to trigger the mails via gmail.We are getting the below error as,

Mail delivery failed via SMTP server 'smtp.gmail.com'.
SMTPAuthenticationError: 535
Incorrect authentication data

(or)

Unable to access account

After restarting the server firewall mails are working fine.We have also checked each and every logs but we couldn't find any issues.Also we have allowed the google IPs in the server.Kindly suggest the steps to fix this issue further.

[hhavci]

Hi,

I have the same problem, can you help me?