This guide helps you resolve an email sending error of the type "the recipient was rejected by the server" / "recipient rejected" (code: 550 5.7.1 relaying denied) or "authentication required" / "proper authentication required".

Troubleshooting a Relaying denied error

Check that the "My outgoing server (SMTP) requires authentication" a bien été activé dans les réglages de votre serveur sortant (SMTP) sur le logiciel de messagerie employé.

You will generally find this setting under one of the following headings:

• "More Settings"
• "Advanced Settings"
• "Outgoing Server (SMTP)"

After correcting this setting, it is important to delete or move the pending messages in your outbox, then try sending a new message.

Using config.infomaniak.com

You can use the Infomaniak configuration tool to help you (log in to your Infomaniak account if necessary).

Also, refer to this other guide for troubleshooting errors.