CiviMail tracking opens stopped working after upgrade to 4.7.x
I've experienced this on a few sites and it turns out the file/directory permissions seem to have changed. I'm not sure if this is in relation to the way 4.7 is packaged, or something on the particular hosts that these sites are on, or what, but I have found that I need to recursively reset permissions after updating, or the tracking doesn't work, click through links don't work, you can't upload images from CiviMail, etc.

From just outside the civicrm directory, I do this and it seems to solve it:

find civicrm -type d -exec chmod 755 {} ";"

find civicrm -type f -exec chmod 644 {} ";"


The first one changes permissions on directories and the second on files.