Error while processing the request! Problem in connecting to the mail server with Ionos Mail

Error while processing the request! Problem in connecting to the mail server with Ionos Mail

Hello.

I want to add a response email with my SMTP.
This is an email that I use at Ionos.

However when I configure everything well, I get this error message: Error while processing the request! Problem in connecting to the mail server

After several searches I do not understand why this error.

Can you help me ?

Thank you.