2015-03-05 11:43:41 fixed_login authenticator failed for (ispip.net) ([XX.XX.XX.XX]) [YY.YY.YY.YY]: 535 Incorrect authentication data (set_id=user@domain.tld)

In cPanel Exim servers, especially ones enabled with SMTP authentication, “535 Incorrect authentication data” is a common error message seen in mail logs. 

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The vast majority of these error instances represent blocked connections from botnets trying to relay spam. This is a security feature to protect the mail server from spam, and cannot be disabled.

However, valid customers might report this error under two circumstances:

1. Incorrect login information

Mail users sometimes enter the wrong format of user name (username vs username@domain.com), or put in the wrong password (especially if the auto-generated password contains too many special characters).

This can give them the error “535 Incorrect Authentication Data” while attempting to send mails with this wrong authentication details, as the mail server cannot validate the login.

Effective solution in such cases is to give them a password easy to remember (but that is also strong – like Halloween=Oct31), and educate mail users on the proper username format.

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2. Corrupted mail folder permissions

‘535 Incorrect Authentication Data’ results when mailbox permissions are changed due to migrations, or an account/server update. This can be quickly fixed by running the ‘/scripts/mailperm’ script from terminal, or by going to:

‘WHM >> Email >> Repair Mailbox permissions’

This error is often reported by mail users who maintain multiple mail devices, and forget to update login details in one of their devices.

With years of experience resolving common causes of all service related errors, our website support team is able to quickly identify the cause and deliver immediate solution for all support queries.

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