Steve,
I'm not sure I am following exactly what you need, but this is what I gather:

You would like to post to a Wordpress blog from an email? You would have an email address you would send a post to and the mailserver would read the email, a script would verify, and then post it to WP for you? Maybe there is a date in the email, or subject line, that WP would also be directed to make the post public?

I had built a system for a newsletter startup idea several years ago that would read emails and extract the content from emails received and save in a database. Your workflow sounded familiar.

Regards,
Eric