Utm Tagging Support
Premailer.Net 1.4 supports utm tagging all hrefs in the markup.
If you add a UtmCampaign string property to your email page, you will get utm tagging on all outgoing links.
This also bumps the requirement for Premailer to 1.4.3, but less than 1.5. See #9 for a report where Premailer 1.3 wasn't backwards compatible, which means we need to keep a stricter version dependency.