We are running Sitecore 8.2 and EXM 3.4 on it.
I just noticed that If I open the email in the web G-Mail client, all image urls are being replaced by google with some proxy.
For example the initial html for pixels that we send look like this:
in G-Mail they all start with https://ci5.googleusercontent.com/proxy/
And it appears that first one - email open pixel with G-Mail proxy'ed url returns 404 by some reason - so in the mailbox I see next picture:
Which also can affect the open email stats in the backend... Is there anything we can do about it? Is it a known issue?