se produit uniquement quand l'évenement a été créer sous thunderbird, ok avec SOGo WebGui.

below the email received by the creator of the event, a "mailto" is in front of the recipient

Sujet : failure notice
Date : 28 Sep 2020 12:25:37 -0000
De : MAILER-DAEMON@mydomain.com
Pour : riri@mydomain.com

Hi. This is the qmail-send program at mydomain.com.
I'm afraid I wasn't able to deliver your message to the following addresses.
This is a permanent error; I've given up. Sorry it didn't work out.

<mailto:loulou@mydomain.com>:
Recipient unknown

--- Below this line is a copy of the message.

Return-Path: <riri@mydomain.com>
Received: (qmail 31062 invoked by alias); 28 Sep 2020 12:25:37 -0000
Delivered-To: alias-localdelivery-mailto:loulou@mydomain.com
Received: (qmail 31059 invoked by uid 453); 28 Sep 2020 12:25:37 -0000
Authentication-Results: mydomain.com; auth=none
Received: from localhost (HELO localhost) (127.0.0.1)
by mydomain.com (qpsmtpd/0.96) with ESMTP ; Mon, 28 Sep 2020 14:25:37 +0200
From: "riri" <riri@mydomain.com>
Content-Type: text/html; charset="utf-8"
X-Sogo-Message-Type: calendar:invitation-reply
MIME-Version: 1.0
Date: Mon, 28 Sep 2020 14:25:37 +0200
Subject: Invitation =?utf-8?q?refus=C3=A9e?= : =?utf-8?q?=C2test
Message-ID: <5b3b-5f71d680-2b-b8d5330@39657126>
To: mailto