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What Gmail's Image Enabling Means to You


By Loren McDonald

[Editor’s note: Google last week announced it would begin serving images automatically in Gmail by caching them on Google’s servers. Since an “open” is recorded when the receiving machine calls for images from the sender, this development will affect open-rate reporting for marketers, but how? Loren McDonald explains:]

Email marketers can expect to see their "unique" open rates start to increase starting today [Dec. 12]. This is because historically many Gmail users will view an email without enabling images - which means the open tracking pixel inserting by email service providers also does not load – along with the images within the email. Because of this (and not just with Gmail – but their huge footprint had the biggest impact on reporting) - open rates for the last several years have been underreported.

• Gmail open rates may now also increase slightly when someone is scanning/going through emails and the tracking pixel loads in a client with a preview pane or the tracking pixel is at the top for the email and loads simply upon scrolling through emails - but the recipient technically never "opened" the email. But this increase is probably very, very small.

• On the flip side, "gross" or "total" opens for Gmail will now be under reported. This is because Gmail will load the images in an email the first time the message is opened by a recipient from the host server (email service provider, client's site, image hosting provider, etc.) - the open tracking image is counted in this scenario. But Google is now caching the image on Google's servers after that initial open and therefore the tracking pixel does not ping the email service provider's servers and so, therefore; any additional opens are not tracked and reported.

• So this aspect of the Gmail change is generally positive. Unique open rates should now be tracked and reported more closely to the actions that recipients are actually taking. Very few marketers actually use gross or total opens, although some email service providers still do report open rates using gross opens – however this is not the standard, industry-agreed upon method. And for a marketer not knowing that someone has opened an email multiple times will have little to no impact. This is because there are very few programs that marketers have built to act on knowing that someone has opened multiple times. There is a metric I call "opens to openers" that is a ratio of how many times people have opened an email divided by the number of people who have opened the message at least once. But it is a niche, rarely used metric that in theory reveals that some subscribers find content in your email of such value that they come back to the email multiple times. So this aspect will again have very little impact on marketers.

• So the biggest concern is around email marketers who utilize services to serve up real-time content (images) that can be different on successive opens – so things like countdown timers, testing images that change once a winner is determined, etc. Additionally, location data will now show as being wherever the Google servers are that are hosting the cached images. Some marketers will serve up unique content to a recipient – say a special event or promotion at a store close to a recipient using the IP data.

Loren McDonald is vice president of industry relations for marketing services provider Silverpop.


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Terms: Feel free to be as big a jerk as you want, but don't attack anyone other than me personally. And don't criticize people or companies other than me anonymously. Got something crappy to say? Say it under your real name. Anonymous potshots and personal attacks aimed at me, however, are fine.

Posted by: Andrew Bonar
Date: 2013-12-18 06:59:19
Subject: Gmail Cache

I do not believe they are respecting cache expiry. However an open on a new device does appear to bypass the cache. The Gmail cache seems to expire after 24 hours. This is relevant to those wanting to serve images that may change after the launch of a campaign. For those who concerned about tracking multiple opens, this appears a very simple issue to resolve. Serving an empty pixel, with content-length=0 provides nothing for Gmail to cache, and therefore every open is recorded. As is the case at several EDM providers. I detailed this in my post here:
Posted by: El Guapo
Date: 2013-12-17 16:52:06
Subject: Caching Behaviour

I think this means that email marketers will need to make sure that their images are served with a shorter cache time. If Google mail is essentially routing everything through their own proxy server, it still needs to follow the rules of caching, just like the proxy server in your office. When the original server sends a file with a cache time of 60 seconds, the next proxy should only cache it for 1 minute. Shouldn't matter if this is an email image or a web background image, it should expire. The tricky thing will be figuring out if Google's proxy follows the rules correctly, and if it enforces its own minimum caching standards.