email tracking image duplicate requests

Question

I am embedding tracking images within emails that are being sent from a custom-built opt-in CRM system. The image src is an encoded .gif, such as src="12_34_675.gif". The image is served by an ASP.NET httphandler that decodes the src encoding and serves a transparent image.

Everything works fine, but some email clients request the image multiple times, creating duplicate entries. Some clients make three calls all within one second, and some seem to make tens of calls over a day or so. Mostly email clients make single calls, but these few duplicates are very perplexing. I know I can code around them, but I'd really like to understand what's going on.

I've checked the IIS log files, which show that the duplicate requests are coming from the client machines. I can't think what might be causing these duplicate http requests.

Help!

Answer 1

I don't think this is something you can control. What if they have an old version of outlook open (older version used to open images embedded in message by default, nice) with the preview pane and pass through your email a few time. I am sure you are not using the tracking data directly from urchin or whatever you are using. Is there a reason the duplicate log entries for the image are a problem?