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List:       postfix-users
Subject:    Re: Intermittent 550 bounced messages
From:       wietse () porcupine ! org (Wietse Venema)
Date:       2013-12-28 0:41:17
Message-ID: 3drmL55fv4zjyms () spike ! porcupine ! org
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Venkat:
> The final delivery address is an Exchange 2010 server.
> The issue we have been experiencing is that when resolving a LDAP alias, it
> will occasionally result in bounced messages with a 550 error. Strangely
> though, this happens to only a very small number of aliases. In cases where
> this occurs, I checked the LDAP server logs and noticed that Postfix does
> not send a search query to LDAP; in successful cases the search query is
> sent. The Postfix logs do not show anything regarding the bounce either,
> the perimeter mail relays and the client simply receive a "550 5.1.1
> <e-mail.alias@domain>: Recipient address rejected: User unknown (in reply
> to RCPT TO command);

Note that Postfix replies with:

    User unknown

    Meaning: the recipient domain matches $mydestination, but the
    user was not found in $local_recipient_maps.

and that Postfix did not reply with:

    User unknown in virtual alias table

    Meaning: the recipient domain matches $virtual_alias_domains,
    but the address was not found in $virtual_alias_maps.

This is consistent with your observation that there is no virtual
alias lookup.

You need to find out why some recipient domains match your mydestination
setting. Maybe this text contains end-of-line comments.  Such
comments are not supported in Postfix.

If you have "show_user_unknown_table_name = no" then that will
complicate trouble shooting.

	Wietse

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