<p>I wrote late last year about changes to how Gmail handles images and the impact for marketers. My thanks to Jordan Cohen of Movable Ink for a heads up on a more recent change.</p><p>You may recall that Gmail started caching images in emails and doing so in a way that had a number of negative impacts for marketing messages, including loss of location, referrer, browser identification, cookies, timing, and total counts. These losses were mitigated by Gmail's subsequent decision to load images by default, thereby increasing counts and improving how most marketing messages looked.</p><p>In a recent change, Gmail has started supporting cache control, a mechanism for websites to indicate how long it's OK to keep content for without requesting an update. While this change does not address all of the capabilities that caching impacted, it does improve the situation for some of them. This is most important to companies that are dynamically serving image content, such as Movable Ink and LiveIntent.</p><p>One might reasonably wonder why the Google cache didn't support cache control in the first place. Web caching has a bit of a checkered history and many websites effectively discourage caching of all their content, thereby undermining the reliability of cache control instructions. It's also possible the Google developers were just being lazy - their original problem didn't require cache control so they never implemented support for it. Whatever the reason, they have relented and now support the cache control header.</p><p><a href="http://www.clickz.com/clickz/column/2333590/gmail-image-caching-update-is-good-news-kind-of">Keep reading...</a></p>