-ERR Logon failure: POP logon failure

Microsoft 365POPSign-in problem

The error usually looks like this:

-ERR Logon failure: unknown user name or bad password.

What it means

Microsoft 365 rejected a POP sign-in. Password sign-in is no longer accepted for POP – only OAuth 2.0 works.

Common causes

  • The app signs in using USER and PASS (basic authentication).
  • The app’s OAuth token is invalid, or POP is disabled for the mailbox.

How to fix it

  1. Switch your app to OAuth 2.0 sign-in, or use Auth-Email if it cannot.
  2. Check that POP is enabled for the mailbox.

Tools to help diagnose it

POP3 connection tester

Use a real POP3 test server to validate your email apps without affecting real data

OAuth token decoder and XOAUTH2 builder

Decode a Microsoft or Google access token, check its scopes, and build or decode XOAUTH2 strings

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 Microsoft 365 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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