Postfix does not send email reply from RT4

hiiii all i need your help
i have Rt4.4.3 work fine with fetchmail for inbound and postfix for outbound
when i send an email to my RT adress i have a ticket created but the email notfy the sender caused a proble

" relay=smtp.xxxxx[x.x.x.x]:25, delay=0.28, delays=0.01/0/0.26/0.01, dsn=5.1.1, status=bounced (host smtp.xxxxxx[x.x.x.x] said: 550 5.1.1 www-data@xxxxx: Recipient address rejected: xxxxxx (in reply to RCPT TO command))
i dont find the problem because my postfix work fine when i test this from command line
thanks for help

This response from a mail server would usually indicate that the email address in question does not exist, or is not able to receive mail.

Hope this helps.

thanks fo reply
this is a big problem i dont find a solution
i’m not be able to send ticket from my RT4 web interface with email using postfix also when i open ticket with mail ther is no reply to requestor it seems an error between postfix and RT4 because postfix work fine when i try to test ti from command line
any one know how made canonical adreess with postfix in order to work with rt4??
please help me

And what happens if you try to send the e-mail from command line but under the user/group that uses your webserver?

hello thanks fo reply
problem resolved with generic file by fixing the sender adress