Is your email application throwing Amazon SES SMTP 535 Authentication Credentials Invalid error?

Amazon offers the Simple Email Service as a quick option to send emails.

However, sending emails often shows authentication errors due to wrong credentials, account suspension, etc.

At Bobcares, we help AWS customers to send emails correctly as part of our AWS Support Services.

Today, we’ll see how we fix the credentials invalid error with Amazon SES.


Where does Amazon SES SMTP 535 Authentication Credentials Invalid error show up?

In general, Amazon SES works as a quick way to send emails from applications. In this model, the user need not have to maintain their mail servers. It allows sending emails from the user’s domain name itself. That’s why many users make use of Amazon SES to send mails.

That raises the question, where do users find Amazon SES useful?

The common scenarios include sending emails from the command line, SMTP mail programs, applications like WordPress, eclipse, etc.

Recently, a WordPress customer reported the SMTP failed error in his email form as:

Amazon SES SMTP 535 authentication credentials invalid


Common causes of Amazon SES SMTP 535 Authentication Credentials Invalid error

Amazon SES uses an SMTP login to authenticate a connection.

Let’s now check the common causes for email failure using SES.


Incorrect SMTP login details

One of the top reasons for SMTP failure can be invalid SMTP login details. Many AWS users provide their AWS IAM username and password in their email application. But, this is different from the SES SMTP login details. For the emails to work, users have to give the correct SES login details.


Special characters in credentials

Similarly, the special characters in SMTP credentials can also create problems while sending emails. The credentials require URL encoding and then provide in the configuration.


Suspension of sending privileges

Likewise, suspension of Amazon Simple Email Service (Amazon SES) can also cause a 535 error. SES is a mail service that has many users. Therefore, Amazon continuously monitors the number of emails sent from each user. If any of the users send bulk emails or spam, there will be resource abuse. This can affect other users on the same server.  Here, Amazon suspends the sending privileges of the suspicious account.

It is always recommended to keep a close watch on your email activity to avoid suspension of service. As a best practice, we always enable authentication with SMTP. In this way, only authorized users can send emails.


How we fixed Amazon SES 535 error?

We’ll now move on and check how we resolved the 535 error with Amazon SES.


Checking Amazon SES status

As the first step, our Support Engineers verified the status of Amazon SES service. This helped us to rule out the possibility of account suspension.


Verifying SMTP login

Further, we verified whether the customer was using the correct SMTP login details.

For this, we logged in to the customer’s AWS account, and selected “AWS Management Console”. Then we opened Amazon SES console.

In the navigation pane, we selected SMTP Settings. In the content pane, we clicked Show User SMTP Credentials. Thus, we could see the current SMTP credentials.

If the user account was found missing, we click on Create My SMTP Credentials. That will automatically create a login with default values.

Likewise, to change your SMTP password, we delete the existing SMTP user in the IAM console. Then, complete the procedures to generate a new set of SMTP credentials.


Validating SMTP connection

Moving on, we validated the SMTP connection from the SES console. It worked fine.

However, the settings in the WP SMTP plugin in WordPress was incorrect. Therefore, we corrected the login details and the error was fixed.

We always make sure to check for special characters in the password.

[Trouble connecting with Amazon SES login? We can help you.]



In short, Amazon SES SMTP 535 Authentication Credentials Invalid occurs due to wrong login details, suspended SES account, etc. Today, we saw how our AWS Experts checked and fixed email sending via Amazon SES.


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