535 5.7.8: Authentication failed

AnySMTPSign-in problem

The error usually looks like this:

535 5.7.8 Error: authentication failed: authentication failure

What it means

The SMTP server rejected the username and password your app sent.

Common causes

  • Wrong username or password, or the username should be the full email address.
  • The provider requires an app password or OAuth 2.0 instead of your account password.
  • The app is using an authentication method the server doesn’t accept.

How to fix it

  1. Re-enter the credentials, using the full email address as the username.
  2. Check which sign-in methods the server offers with our email server checker.
  3. If the provider requires OAuth and your app can’t use it, use Auth-Email.

Tools to help diagnose it

Email server checker

Check any IMAP, POP or SMTP server’s encryption, certificate and supported sign-in methods

SMTP connection tester

Spin up a real SMTP test server and diagnose your email sending configuration in real time

Can’t update your app to use OAuth?

Auth-Email fixes sign-in errors like this one without changing your app, printer, scanner or script. It signs in to your email provider with OAuth on your app’s behalf, while your app keeps using a normal username and password over IMAP, POP or SMTP.

Read the docsTry Auth-Email →

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