Solve an error Sender Mismatch

This guide presents messaging authentication mechanisms and ways to resolve the error Sender Mismatch.

Preamble

• The "Sender Mismatch" error occurs when the address used to send an e-mail does not match the authentication address used when connecting to the SMTP server.
• This error is linked to two specific elements:
  • on Return-path (also called "envelope sender"), which is used by the mail server to manage returns and delivery errors,
  • and the header From, which is the sender address visible by the recipient in the message.

Solve the Sender Mismatch error

Technically, when sending an e-mail via a software/mail client, you need to authenticate using a username (= your e-mail address) and a password.

If, after authentication, the sender address specified in the header "From" or in "Return-path"is different from the address used for authentication, the Infomaniak server can consider this as an attempt to falsify. It is this inconsistency that triggers the error "Sender Mismatch".

To correct this error:

• Check that the email address used for the shipment is the one with which you authenticate yourself (or a valid alias).
• Do not change the address Return-path or the heading From for another unauthorized address (if necessary, be aware of this other guide to test another email application or to properly configure your current email software/client).