Postfix reject_unverified_recipient question

[Peter Ong]

Hello Everyone,

I know this is a MailScanner list, but in the off chance there's a postfix expert here, I'll venture to ask.

In my postfix installation, I have enabled this:
reject_unverified_recipient

This postfix is the MTA for our MailScanner gateway. With said option enabled, it takes the recipient and verifies it exists with the final destination mail server. If that server says that address exists, then the gateway will proceed to receive the rest of the email. However, when the recipient is one that does not exist, the final destination server replies a 550 etc. The gateway then replies to the sending SMTP server with a 450. This is bad because with a 450, many mail servers will not let the senders know until after 5 days have past that the email couldn't be sent.

I need the gateway (postfix) configured such that when the final destination server replies with a 550 when verifying the existence of an address, that it will also reply a 550 to the sending email server. Would there be an postfix experts on the list that could shed some light on this? Thank you.

p