Sending emails is a critical feature for most Laravel applications. Whether it’s account verification, password reset, or notifications, email delivery must work reliably.

However, many developers face the following error when configuring AWS SES with Laravel:

SMTP Error 535: Authentication Credentials Invalid

This article explains why this error occurs, what it actually means, and how to fix it permanently in Laravel.

Understanding the Error

The full error usually looks like this:

Failed to authenticate on SMTP server using authenticators LOGIN, PLAIN.
Expected response code 235 but got 535.
Authentication Credentials Invalid.

What does this mean?

• Laravel successfully connects to the SMTP server
• The SMTP server rejects the username or password
• Authentication fails before sending any email

This is not a Laravel bug.
This is almost always a configuration issue with AWS SES SMTP credentials.

Why This Error Happens (Most Common Reasons)

1. Using IAM Access Keys Instead of SMTP Credentials

AWS SES does not accept normal IAM Access Key & Secret Key directly for SMTP authentication.

Many developers mistakenly copy:

• AWS_ACCESS_KEY_ID
• AWS_SECRET_ACCESS_KEY

and paste them into:

MAIL_USERNAME
MAIL_PASSWORD

❌ This will always fail with a 535 error.

2. Wrong AWS SES Region

AWS SES is region-specific.

If your SES is created in:

• ap-south-1 → you must use
  email-smtp.ap-south-1.amazonaws.com

Using the wrong region host causes authentication failure.

3. Special Characters in SMTP Password

SES SMTP passwords often contain:

• +
• /
• =

If the password is not wrapped in quotes, Laravel may parse it incorrectly.

4. Laravel Config Cache Still Using Old Values

Laravel caches configuration aggressively.
Even after fixing .env, Laravel may still use old credentials.

Correct Way to Configure AWS SES SMTP in Laravel

Step 1: Generate AWS SES SMTP Credentials

Do not use IAM access keys.

1. Go to AWS Console
2. Open Simple Email Service (SES)
3. Navigate to SMTP Settings
4. Click Create SMTP Credentials
5. AWS will generate:
   • SMTP Username
   • SMTP Password

Save them securely.

Step 2: Update Laravel .env File

MAIL_MAILER=smtp
MAIL_HOST=email-smtp.ap-south-1.amazonaws.com
MAIL_PORT=587
MAIL_USERNAME=YOUR_SES_SMTP_USERNAME
MAIL_PASSWORD="YOUR_SES_SMTP_PASSWORD"
MAIL_ENCRYPTION=tls
MAIL_FROM_ADDRESS=contact@yourdomain.com
MAIL_FROM_NAME="Your Website Name"

Important Notes

• Always wrap MAIL_PASSWORD in double quotes
• Ensure MAIL_HOST matches your SES region
• No extra spaces before or after values

Step 3: Clear Laravel Cache (Very Important)

Run these commands on your server:

php artisan config:clear
php artisan cache:clear
php artisan config:cache
php artisan route:clear

If you are using queues:

php artisan queue:restart

Verifying Email or Domain in AWS SES

AWS SES requires verification.

You must verify either:

• The sender email address
  OR
• The entire domain

If not verified:

• Emails will fail later with different errors (not 535)
• In sandbox mode, you can send emails only to verified addresses

Common Mistakes to Avoid

• Using IAM keys instead of SMTP credentials
• Forgetting to clear Laravel config cache
• Using wrong SES region hostname
• Leaving APP_DEBUG=true in production
• Exposing SMTP credentials in public error pages

Production Security Best Practice

Always disable debug mode in production:

APP_ENV=production
APP_DEBUG=false

This prevents:

• Credential leaks
• Stack trace exposure
• Security risks

Final Checklist

Before testing again, confirm:

• SMTP credentials are generated from AWS SES
• Correct region SMTP host is used
• .env password is quoted
• Laravel cache is cleared
• Sender email/domain is verified in SES

Conclusion

The SMTP 535 Authentication Error in Laravel is not a framework issue.
It’s a credential mismatch caused by incorrect AWS SES configuration.

Once you:

• Use proper SES SMTP credentials
• Match the correct region
• Clear Laravel cache

the issue is resolved permanently.