live.com is marked my email as junk, when i open mial in junk folder, open stats counting. mail is in gmail inbox and no problem.
All mail reads by Mac mail.app or ms outlook 2013. But some other domain (e.g. tekur.com) cant send open stats. There is no any restriction to download external images all email clients.
Problem solved in mail server side. Some mail server with spam controller is (like mailscanner) blocking tracking pixels (like 1x1spacer, space.png etc) and replacing with their links. After the disable this option in MailScanner, problem solved.