Thanks for your advice!
We actually convert all links in your HTML newsletters to use our own tracking URL's such as yourname.createsend(dot)com. This way you can see a nice report on which links were popular and at the same time the URL won't be accessible in the source.
Of course, unless you plan on publishing your emails on your web site, there is no way they will get indexed by spiders if they remain only in your subscribers inbox.
That's great, thanks. I was just afraid that the online version of the e-mail at createsend.com might be vulnerable.