Images src changes after update

Hi
I’m using images hosted on Amazon under different domain than my site. When I edit newsletter campaign everything looks ok but after I save my changes all image src urls are changed from http://www.imagedomain.com/something/image.png to http://www.mydomain.com/something/image.png.
I’ve checked that “embed images” is off but no progress.
Can you please help ?
regads !