Windows SMTP Relay Server to add BCC to all emails

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http://serverfault.com – I'm looking for a Windows based SMTP Relay Server which allows me to add a specific BCC field to all outgoing emails that relayed through this server. The reason for such requirement is that we need to track if the email is actually sent. We're sending our email to end users via our cooperate email server. Currently we're receiving complaint that our end users did not receive our emails, but we don't have access to the email server's log. At the same time, our developers are using a specific library which doesn't allows adding BCC, or it's much more tedious to do so than replacing our SMTP (HowTos)