No one like addressing the email aspect of an application because of the many nuances involved ... yada yada. ... I've been nursing the idea of outsourcing email from within my SaaS applications by delegating the sending and tracking of email using APIs of popular email campaign service providers e.g. CampaignMonitor, MailChimp and MadMimi.
Although I vowed not to work over the weekend, I ended up creating WWW::MadMimi for the Perl community which currently live at GitHub.