>I have been unable to determine what exactly are the limits that gmail puts on sending email like this.
>
>One page says 500 per 24 hours if using the web interface, 100 for IMAP/POP.
>
>Other places I have seen 200 per hour.
>
>Does anyone have the real figures and any suggestions how to get around this problem?

I tried doing the same thing at one point and eventually gave up on it. Now I use smtp relay services.

I have used http://www.authsmtp.com/ for years now. Just be sure to update your mx record for the IP assigned by your smtp relay and then you're good to go.