IT Toolbox
Guide

How to correct Sender mismatch with an authenticated SMTP

The name of the user is given in the form of the name of the user.

TopicIT Networking →
⌚ About 2 min read
View my favorites
Email / SMTP Intermediate. 10 min

The name of the user is given in the form of the name of the user.

Avant de commencer : adaptez toujours les commandes et manipulations à votre environnement. Sur un système de production, prévoyez une backup ou un retour arrière lorsque l’action peut modifier la configuration.

Étapes à suivre

  1. 1

    Remove the complete error

    Discard the 550 and the exact text returned after Data.

  2. 2

    Identify the authenticated account

    Note the address used for LOGIN/AUTH.

  3. 3

    Compare From

    Check the, address of sender configured in WordPress or the application.

  4. 4

    Test the alignment

    Temporaryly use exactly the same address for authentication and From.

  5. 5

    Configure the Alias if necessary

    Add or authorize the Alias supplier side before re-use.

À retenir

  • SPF or DKIM do not correct unDeferer mismatch when submitting SMTP.
  • The Return-Path can also be controlled by some suppliers.
  • In WordPress, force the From only if the address is actually allowed.
← All les guides
Technical deep dive

SMTP: distinguish authentication, envelope and visible identity

Technical checkpoints

  • The authenticated SMTP user, MAIL FROM and From: header can be three different identities.
  • A Send As / sender mismatch error occurs when the server accepts authentication but rejects the requested sender identity.
  • Message-ID, Return-Path and Received headers help reconstruct the actual message path.

Reading a failure

Keep the full SMTP response code and compare authenticated account, envelope sender and visible From.

AUTH user@example.com
MAIL FROM:<sender@example.com>
From: Display <sender@example.com>

Topic-specific pitfalls

  • Changing SPF/DKIM does not fix a missing Send As permission on the server.
  • Testing with another sender without keeping the exact response code can hide the true scope.

How to validate

  • The server accepts the expected sender with the intended identity and permission.
  • Received message headers match the expected account and domain.
♡ 0