I'm running 10.6.8 and I set up a smart mailbox with two conditions: one, to look in a specific folder, and two, to match any recipient = email@example.com.
Mail.app doesn't seem to search the entire actual email message. Neither does Spotlight, which might be the crux of the matter. And so I can't search for the envelope-recipient address in some messages, and that routing address does sometimes differ from the header-recipient (the one in the To: field).
It may help, in this case, to consider an email as being similar to a physical envelope. The front of the envelope contains routing information, handled by the mail-transfer agent (e.g. sendmail, postfix, qmail, Exchange). The inside letter contains formal addresses handled by the reader, which in this case is the mail client.
So, Mail.app doesn't necessarily have to care about the routing info -- the envelope-from address, which is Return-Path:, and the envelope-recipient address, which is shown in the Received: header -- it just cares about the To:.
Any ideas? Example header below where env-rcpt address differs from header-rcpt.
Return-Path: <firstname.lastname@example.org> Received: from mta.bar.com (mta.bar.com [126.96.36.199]) by mta.foo.com (8.14.5/8.14.5) with ESMTP id xA123abc012345 for <email@example.com>; Thu, 3 Nov 2011 01:01:51 -0500 (EST) (envelope-from firstname.lastname@example.org) Message-ID: <email@example.com> Date: Thu, 03 Nov 2011 06:56:48 +0100 From: Sender <firstname.lastname@example.org> To: Recipient <email@example.com> Subject: Hello!