I am receiving emails from a text box on my website but when they arrive in my inbox they are from a postmaster address as opposed to the senders email. Unless they put their address onto the the emailed text I have no way of replying to their enquiry. Is there any way for me to find the senders address to enable response?
The email that you are recieving is not actually being sent from the submitters mailbox but from the webserver that your website is hosted on. Therefore the messages are going to be delivered in to your mailbox using the mailserver email address. This unfortunatly can not be changed.
how can i regain e.mail rejected for wrong address
That depends on how the sender was. If it was a message you sent you should be able to find it in a sent messages folder. If it was sent by someone else they would see a bounceback alerting them that they had the incorrect address and would have to retrieve the message themselves.