Image Blocking in Email Clients and Web Services

Handy graphs and best practices on the state of default remote image loading in desktop and online email clients -- a problematic issue from a security point of view, and a marketing heaven from an advertising perspective :

"Every client has its own default settings regarding displaying/hiding images. And while most email clients have a setting to turn images on or off, some offer conditional settings which are contingent upon known senders or other factors. The following table outlines the default settings of popular desktop- and webmail-clients."

Sometimes a spam email isn't sent with the idea to trick someone believe into something, but to act as a verification of that email's existence in the form of remote image -- web bug -- loading, and yes it could also act as a redirector to pretty much anything malicious. Go through related posts in case you're interested, and also see a common trade-off image spammers face.