The error “550 5.7.1 authentication required” usually happens when an Email client cannot connect to an Email server.

Email clients like Microsoft Outlook, Mozilla Thunderbird, Eudora, Mailbox connect with Email servers to organize mails.

This is a common error faced by our clients and let’s see how our Support Engineers fix this error.

How and Why the 550 5.7.1 authentication required error happens?

An Email client is an application used to organize mails easily. This includes sending, receiving, creating, organizing and discarding mails.

Usually, Email clients like Microsoft Outlook, Mozilla Thunderbird use SMTP (Simple Mail Transfer Protocol) to connect with an Email server.

While connecting to an Email server, firstly Email client authenticates the user. This error happens when a user fails to connect to the Email server using SMTP.

Users authenticate with an Email address and password to prevent spammers from reaching your Email server.

Now let’s see the error code “550 5.7.1 authentication required” in detail. The error code has three parts:

• Reply code 550: A permanent error that denotes a mail system status.
• Status code 5.7.1: A permanent failure due to unauthorized sender.
• Reply text authentication required: The error in human-readable form.

So far we have seen the details of the error. Now let’s see how our support engineer fixes this issue.

How we resolve 550 5.7.1 authentication required error

“550 5.7.1 authentication required” is a common Email client error. When our customers face this error, our Support Team looks for the Email logs at our server-side. This is one of the best options to know the cause of the error.

If the Email server has a cPanel, then our Support Team checks for /var/log/exim_mainlog to know the error.

There are two possibilities for this error.

1. Incorrect login details

Some users give incorrect user name and password while configuring an Email client. This can be typing errors like extra space, typo errors in entering user details, etc.

We ask our customers to double-check for the details given while configuring an Email client. Usually, this is the most important issue causing this error.

2. Configuration details of Email client

Usually, configuration details also result in Email errors. The configuration details vary for different Email clients. The user should enable the option for authentication in every Email client.

Therefore, we ask the customer to check the configuration details that each Email clients ask for. Like enabling the checkbox “My server requires authentication” in Microsoft Outlook.

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Conclusion

In short, the error “550 5.7.1 authentication required” is an SMTP error. This occurs when there is a validation failure at the sender’s side.Today, in this article we saw an Email error, the common reasons for the error and how our support engineers fix this issue.