I'm evaluating Campaign Monitor, Constant Contact and Mail Chimp to host a little "add your email" form on our website, then run email marketing campaigns against the addresses collected.
I've evaluated the competing products on cost, data portability and endorsements, but I'm stuck trying to evaluate how "secure" and how "reliable" (uptime/SLAs) each option is.
None of them offer specific SLAs -- just broad "we'll do our best to keep it up" language, and I can't find a source for historical uptime data. For security, again there's no language in their TOS that help, just "we'll do our best."
Even if you don't have any experience with these tools, I'd appreciate your opinions on how to evaluate any web service against these criteria.