Hi@ADB59 ,
Thank you for your question.

My colleague@martin.frydl tested your use case and he was not able to replicate the issue that you had described.
It sends an email with single To header with two addresses which is compliant with RFC 5322:
The destination fields of a message consist of three possible fields,each of the same form: the field name, which is either "To", "Cc", or "Bcc", followed by a comma-separated list of one or more addresses.

The messages are:

Received: from localhost (localhost t127.0.0.1])
        by fake-smtp-5bdfb98bdc-9q8zt
        with SMTP (SubEthaSMTP 3.1.7) id L6KVEXYT;
        Mon, 08 Aug 2022 14:50:38 +0000 (UTC)
From: here@home.cz
To: hello@home.cz, there@there.com <----------------- two comma-separated addresses here
Message-ID: <287742770.34.1659970238693.JavaMail.martin.frydl@klokan>
...

It was tested on version 13.9.

Hi @Adela Sotonova ,

We use Ataccama DQC version 11.0.0 and, when we use a task “SendMail” in a workflow, and if we set up several recipients, the mail generated contains several “to” header.

Ataccama generate this mail :

when we should have only 1 line “To” with the recipients list.

Hi @ADB59 ,

I would like to kindly ask you to go to the Ataccama Help Center and click on Create a ticket to create a ticket to the Ataccama Support team. Provide as much details as possible in the ticket summary like the version you are working on, screenshots of the error, relevant logs, etc. Our Support team will be happy to assist you promptly.

Thank you,

Adél