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I assume this means that google is caching images only on demand, when the user opens the email first and only then. Otherwise there is no way for them to track

I assume this means that google is caching images only on demand, when the user opens the email first and only then. Otherwise there is no way for them to track the first open.

tijs 13y ago
yeah i was wondering that as well. if they tested 'around the office' as the post seems to indicate they might have missed the effect that for every extra person that opens an email the picture is coming from google's cache and thus the open is not counted.
- dangrossman 13y ago
  > for every extra person that opens an email the picture is coming from google's cache and thus the open is not counted Each e-mail has a unique image URL; Google has to make a request for each individual mail even if they're caching images.
  - tijs 13y ago
    ok makes sense. a file hash might fix that and save google some bandwidth but i imagine they do not want to break tracking completely for now...
    - dangrossman 13y ago
      To hash the file you first have to download it. Downloading it is the tracking action, not showing it. Deduplication does not affect open tracking pixels.