Hi,
Thank you for your answers.
@takayukister : I’ve tested with another email address (with different domain name in case of spaming or blacklisting). It works through Post SMTP for ex, but contact form 7 still shows the orange ‘spam’ alert.
@buzztone : like written before I’ve already tested without any captcha and encountered the same issue https://www.agencewebdigitale.com/test/