I have a domain that is hosted elsewhere, on an email-only account. There is no site, just email. But I get so much spam. It doesn't make any difference whether you have a site or not. Spam will come!
Regarding your policy of "Domain EMail being bundled with web site services or forwarding". I willll make a case against that decision.
I recently participated in a fairly "long" mailing list discussion about spam. One participant was adamant in asserting that domains that "do not" have a web site get far less spam. Or at least far less spammer guessing at addresses, such as fred@, joe@, pete@, and all the common names.
His theory was that spammers are reaching for the most convenient low hanging fruit. Figuring that if the domain had a web site, it was worth making the effort to hammer at the EMail server.
Our domain email is bundled with our web hosting packages. Your domain is set to forward to another website. So if you want to keep that setting, you can purchase web hosting/email with us and just set the Mail Host MX record in the Domain Forwarding server selection box to our web host server. Though you wouldn't get much use out of the website hosting portion of the package...
You can purchase web hosting with email here: http://www.dynadot.com/web_hosting/about.html