I entered the SMTP informations to send the autoresponder from my own e

Please note that our system does not check the correctness of entered SMTP credentials. In other words, even though you enter wrong credentials, your email is added as a sender email. On the other hand, when your form is submitted, if the SMTP credentials as wrong, sender email returns automatically to noreply@jotform.com. 

So, I can suggest you to check your credentials and try with the right ones. 

Thank you very much and please excuse my fault. I checked host, username and passwort multiple times, but the Security Protocol was wrong. No it works fine! :)