Send & Receive Issues

How to Fix Gmail Error 535 Authentication Failed When Sending Email

Natalie Taylor Oct 15, 2026 869 views

Question details

The user is unable to send outgoing messages and needs to resolve an authentication error preventing email delivery.

How to Fix Gmail Error 535 Authentication Failed When Sending Email

Product: Gmail
Device & OS: not provided
Scenario: Attempting to send an email using a third-party email client configured with a Gmail or Google Workspace account.
Observed behavior: The email fails to send, returning Error 535 Authentication Failed, and often prompts the user to update client settings to Microsoft Exchange.

Before you start

Ensure you have your current Gmail password or a generated App Password ready, and verify that your device has an active internet connection before modifying your email client settings.

Solution 1Recommended

Verify and Update Your SMTP Authentication Settings

Incorrect SMTP server credentials or outdated authentication methods are the most common causes of Error 535.

Email clients require specific outgoing server configurations to securely connect to Google's servers. If your password was recently changed or if the authentication protocol is outdated, the connection will be rejected.

Access account settings

Open your email client, navigate to the Account Settings or Preferences menu, and select your Gmail account.

Locate outgoing server settings

Find the section labeled Outgoing Mail Server (SMTP) and click on advanced settings or edit server properties.

Update server and port details

Ensure the server address is exactly smtp.gmail.com. Set the port to 465 for SSL encryption or 587 for TLS encryption.

Verify authentication credentials

Check the box that says 'My outgoing server (SMTP) requires authentication' and ensure your full Gmail address and current password are entered correctly.

Verify and Update Your SMTP Authentication Settings

Google App Passwords: If you have 2-Step Verification enabled on your Google account, your standard password will not work. You must generate a 16-digit App Password from your Google Security settings and paste it into the SMTP password field.

Solution 2

Reconfigure the Account as Microsoft Exchange

If the error specifically requests updating to Microsoft Exchange, your email profile may be incorrectly identifying the server connection type.

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Frequently Asked Questions

Why does Gmail Error 535 mention Microsoft Exchange?

This usually happens when an email client, particularly Microsoft Outlook, attempts to route a Gmail or Google Workspace connection through legacy Exchange protocols incorrectly, or if there is a conflicting Exchange alias in your setup.

Does changing my Gmail password cause Error 535?

Yes. If you recently changed your Google account password but did not manually update it in your email client's outgoing (SMTP) server settings, the client will fail to authenticate and trigger this error.

How do I fix Error 535 if I use 2-Step Verification?

Navigate to your Google Account security settings and search for 'App Passwords'. Generate a new 16-digit password for your specific email client, and paste that password into your client's SMTP authentication settings instead of your regular password.

Outlook & Email Problems