Mail appeared to be SPAM or forged

[ephigenie]

this <helo=oproxy5-pub.bighost.com> seems to be not listed as an official MX for the domain <from=myofficemail@mycompany.com>

So its not configured the right way.
And because someone tries to send mail from a domain who's not the MX of that domain its one of the most common methods of spammers (i.e. forging being someone you're actually not ... ) so policyd behaved perfectly right.

If they're using a proxy or cluster to deliver outgoing mails - this cluster must be hidden behind valid MX entries ( hidden because otherwise each hostname has to appear in each dns zone as a valid MX)