I'm using Typo3 powermail mail forms, after send the form is stored in backend but never send a copy to the recepient or user adress. how can i troubleshoot this issue ? btw, Test emails from installtool works good.
Did you configure your form that it uses the email address of the visitor who fills in the form as sender address? That's not good practice anymore. Most mail servers check the SPF record and reject mails that don't pass that test.
You can configure the default sender name and address via TypoScript. And check if the SPF Record fits for that sender address.