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Resolve "550 5.7.1 relaying denied" error
This guide helps resolve a mail error of the type "the recipient was rejected by the server, server response 550 5.7.1 relaying denied" or "Proper authentication required".
Resolve a Relaying Denied Error
Ensure that the "my server requires authentication" setting is enabled in the outgoing SMTP server settings in the email software you are using. You can find this setting in the software you are using under a section like "Additional Settings" or "Advanced Configuration" under Outgoing SMTP Server.
After correcting this, delete/move any pending outgoing messages and try with a new message.
We recommend using https://config.infomaniak.com to properly configure your application. Also, read this troubleshooting guide.
If the error mentions "IP name possibly forged" instead, it will be necessary to check the situation with the responsible party for your IP address.