I found GMail will block the mail without send from information. But GMail will automatic return mail to the sender, not the replay mail(relay mail is provided by the user.). (I think this is it's bug)...

Is it possible to auto assign return path to the sender mail automatically to avoid the blocking issue? Thank you~~

this might be a GMail bug, but I don't see which auto assignment you propose, Eric? 

I know send from and send to can configure in the feedback's setting. But if I don't input the send from information, I found GMail will block my e-mail. In order to avoid GMail block my e-mail, I need to fill the "send from" information in the feedback setting. In general, I will input my e-mail address because I don't know the user's e-mail address.

Then I found another issue, when I reply the mail in the GMail. The reply address is my e-mail address not user's e-mail address. So I will receive the reply e-mail if I don't change the reply address when I reply the feedback mail. If I use outlook express, everything work fine, so I think this is GMail's bug so I want to know is there any way to work around this problem..

Thank you~~