Hey Siebe
did you follow the following instructions? https://support.smartbear.com/readyapi/docs/functional/steps/send-email.html
I'm surprised about the ZERO traffic in fiddler - this would make me think the config in ReadyAPI is completely wrong if it's not sending any traffic at all..
Did you monitor the ReadyAPI log, HTTP log and the Error logs whilst submitting the test step?
If not - can you retry and publish the content of these logs - they may reveal the cause of the problem hindering the request working.
I do know a couple of years back - this Send Mail teststep could only deal with basic authentication on mailboxes - but ive just had a look at the instructions and I think they've gotten past that now.
Cheers,
Rich