Are complaint mails effecting our server?

Best,

We use your servers to send emails with Sendy. Sendy's website states that it uses your servers for sending emails.

However sendy is installed on our domain: sendy.simple-simon.net so we wonder what happens with a complaint mail. Does a complaint mail have a direct or indirect negative effect on our own servers (possibility of blacklisting)? Or is our own server completely separate from this and unaffected?

We would like to receive a clear answer to this.

Sincerely,

Sedat Ayar