Accept mail with attachmnet from known e-mail address

Hi, I would like to allow mail from a known e-mail address say a...@example.com with an attachment say X to a user in my domain say u...@kenkob.co.ke ,but at the same time reject another e-mail from an e-mail address different from a...@example.com to u...@kenkob.co.ke with attachment X. How do I

Relay mail to another postfix host

Is it possible for me to configure postfix to forward/relay mail to another host within the same domain without bouncing the mail with undeliverable errors? Regards, Stephen

RE: Multiple users and multiple servers

I have a somehow related problem. My mail server uses lmtp:unix:/opt/insight/var/imap/socket/lmtp to transport mails. I want postfix to forward or redirect a mail for a user in my domain (e.g. [EMAIL PROTECTED] )to another user in test server am currently configuring e.g [EMAIL PROTECTED] At the t