This plugin for the iPhone and iPod Touch allows you to block HTML and Images in the e-mail reader that come from internet sources. This is very helpful at preventing spammers from knowing your mailbox is active (even without you doing anything but watching the mail), it also helps keeping bloated images from your mail when you dont want to see them.

The plugin does not block internal images and attachments that are self-contained in the message itself (Spammers can't know about those stuff anyhow, unless you actually click on them or so).

This plugin requires a JailBroken phone to work, and if you want to control it being on or off you need to install SBSettings (if you don't it's ok, but the plugin will always block the content until you remove it or install SBSettings). Under SBSettings you should have a toggle called ImageBlock, turning it on will block content, and turning it off will not (you'll have to visit another message and go back to the current one to see the images).