I'm not saying this isn't a good idea, but really, having RSS trigger an email is really a trivial and commonly available service from dozens of free third-party sites, why not in the meantime avail yourself of that? There's even ones that will trigger an email based on edits to a page - in your case I would suggest this one
http://www.dokuwiki.org/security
Also, if you already subscribe to the mainstream security vulnerability notification services, just set up a filter on the packages you're involved with - anything major involving DokuWiki will show up there, e.g.
http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2011-2510.