Infomaniak / SMTP error code 550
smtp;550 5.7.1 rejected by DMARC policy for example.com (in reply to end of DATA command),
The sent message failed the DMARC policy for the sending domain. If the sending domain has a reject policy set for DMARC, the message must pass DKIM or have SPF aligned to the domain with a custom Return-Path. To resolve this, you'll need to contact your email service provider to see how to send a message that passes DMARC support.