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Here’s what causes “535 Incorrect Authentication Data” in cPanel Exim servers and how you can solve it

by Visakh S | May 16, 2015 | cPanel

Please Note: This article is part of our historical archive. Because it was published a while ago, some of the information, links, or context may now be outdated.

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 ([email protected])

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

See how our website support experts help you!

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 [email protected]), 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.

[ You don’t have to lose your sleep over lost emails. Get our professional help to fix your mail errors at affordable pricing. ]

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.

[ Need help resolving email errors in your sites? Get assistance from our website experts to fix all your website errors instantly. ]

Related posts:

    1. How to resolve “550 Access denied – Invalid HELO name” error from Outlook (0x800ccc78), Windows Mail, etc in cPanel/WHM Exim mail servers
    2. 2 non-obvious reasons for “550-Please turn on SMTP Authentication” error in cPanel & Exchange servers, and what to do about them
    3. Missing sent mails in iPhone or iPad? Here’s how you can sync IMAP folders in cPanel and Plesk mail accounts
    4. Resolving Outlook error 0x80042109 in cPanel/WHM web hosting servers

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