Sometimes, when trying to log in to your mail server, you may see an error saying "SMTP Error 535 Authentication Failed." This happens when the server cannot verify the username and password you entered. Let’s look at what causes this error and how you can fix it.
SMTP (Simple Mail Transfer Protocol) is used to send emails. If the server detects incorrect authentication details or settings, it shows this error. The error message may vary depending on the email client you're using. Here are the most common reasons:
If you enter the wrong username or password, the server won’t let you log in.
For most email accounts, the username is the full email address.
Some servers may require different login details for security. Check with your email provider if you’re unsure.
Your account might be temporarily or permanently disabled because of:
Spam activity
Payment issues
To fix this, check your account status and contact support if needed.
Some servers require encrypted connections (SSL/TLS).
If encryption is turned off, you may see this error. Make sure SSL/TLS is enabled in your email client.
Your email client might use a method that the server doesn’t support.
For example, expired or disabled IP-based authentication could cause this error. Contact support to confirm your account settings.
Here are some steps you can follow to resolve the issue:
Log in to your control panel and check if your account is active.
If there’s an issue, you may get a notification or alert.
Double-check your username and password.
Update your credentials to a strong and secure combination. Remember to save these for future logins.
If someone is trying to access your account repeatedly, block their IP address in your server's firewall. This can stop unauthorized access.
SMTP authentication is needed to send emails. Here's how to enable it:
Log in to your Plesk control panel.
Go to Tools & Settings and click on Mail Server Settings.
Under Relay Options, select Enable SMTP Services.
Open WHM and go to Service Configuration.
Select Service Manager.
Check the box for Antirelayd
SMTP Error 535 usually happens because of incorrect login details or account settings. The most common fix is to check and update your credentials. If the problem continues, you can follow the steps above or contact your server support team for help.
If you’re still facing issues, feel free to reach out to a server management service provider for expert assistance.