Django Allauth login/signup fails with SMTPAuthenticationError (535) in production

I’m experiencing an issue in production where login and signup fail due to an SMTP authentication error when using Django Allauth.

❗ Error

SMTPAuthenticationError: (535, b'Incorrect authentication data')

Relevant traceback:

File ".../django/core/mail/backends/smtp.py", line 97, in open
    self.connection.login(self.username, self.password)

File ".../smtplib.py", line 669, in auth
    raise SMTPAuthenticationError(code, resp)

Environment

  • Django: 6.0.3

  • Python: 3.14.3

  • django-allauth: latest

  • Deployment: cPanel (Passenger)

  • OS: Linux (RHEL-based)

Email Configuration

EMAIL_BACKEND = 'django.core.mail.backends.smtp.EmailBackend'
EMAIL_HOST = 'mail.agrotekpluss.com'
EMAIL_PORT = 587
EMAIL_USE_TLS = True
EMAIL_USE_SSL = False

EMAIL_HOST_USER = config('EMAIL_HOST_USER')
EMAIL_HOST_PASSWORD = config('EMAIL_HOST_PASSWORD')

DEFAULT_FROM_EMAIL = 'atpsus@agrotekpluss.com'

Allauth Settings

ACCOUNT_EMAIL_VERIFICATION = "mandatory"
ACCOUNT_LOGIN_METHODS = {'email'}
ACCOUNT_SIGNUP_FIELDS = ['email*', 'password1*', 'password2*']

Steps to Reproduce

  1. Go to /accounts/login/ or signup page

  2. Submit valid credentials

  3. Allauth attempts to send verification email

  4. Request fails with SMTPAuthenticationError

Actual Behavior

  • Login/signup fails

  • Email is not sent

  • Exception is raised during SMTP authentication

Expected Behavior

  • User logs in or signs up successfully

  • Verification email is sent

What I’ve Observed

  • The issue only happens in production

  • It occurs specifically when Allauth sends a verification email

  • If I disable email verification, login works:

ACCOUNT_EMAIL_VERIFICATION = "optional"

Question

What could cause (535, b'Incorrect authentication data') in this setup?

  • Could it be incorrect SMTP credentials or host mismatch?

  • Does the SMTP server need additional configuration for TLS/auth?

  • Are there known issues with Django 6 / Python 3.14 and SMTP?

Additional Notes

  • SMTP is configured on port 587 with TLS

  • Using environment variables for credentials

  • No issues locally (only in production)

Any guidance on debugging or fixing SMTP authentication in this context would be appreciated.

Everything looks good so I'm thinking this is probably an issue with your host. Since you didn't have any issues in development, what email host did you use in dev? Can you try with another SMTP client?

Also confirm from your host provider if the email host is actually:

EMAIL_HOST = 'mail.agrotekpluss.com'
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