Hello I have created a form that work well. But i have an issue in Front End. If i filled the form as user and put gmail, company email, outlook as my email, the site owner can received my request email as well as user i received a copy. But if I put a yahoo email as my email, site owner don't received the mail but as a user I received a copy and a Mail delivery failed: returning message to sender it seems that Rsform pro is using the user email to deliver email to site owner.

This is the message i received.

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its
recipients. This is a permanent error. The following address(es) failed:

............................@gmail.com
host gmail-smtp-in.l.google.com [173.194.197.27]
SMTP error from remote mail server after end of data:
550-5.7.1 Unauthenticated email from yahoo.com is not accepted due to domain's
550-5.7.1 DMARC policy. Please contact administrator of yahoo.com domain if
550-5.7.1 this was a legitimate mail. Please visit
550-5.7.1 support.google.com/mail/answer/2451690 to learn about DMARC
550 5.7.1 initiative. r93si8149693ioi.133 - gsmtp

Thank for help as for me it an urgent issue because user with yahoo email will not be able to send email to site owner

Most free e-mail companies has Mail Protection features like DKIM and DMARC Policies.
Nowadays it's not advised to send e-mail out of the customer name, due to SPAM policies.
The best way to do this is to use a noreply address on the sender field and use the reply-to field for the correct address to reply to.

So in Admin mail you use
Sender - Noreply@....
Reply To - EMail value field