yahoo mail converts img height to min-height

Images are distorted in Yahoo Mail as it, for some reason, chooses to convert height into min-height.

I've done as instructed here but that does not help. Neither does this question.

This is the code for the img tag.

max-width:100%;height:auto;display:block;margin:20px auto;

And this is what Yahoo decides to do according to Firebug:

element {
max-width: 100%;
min-height: auto;
display: block;
margin: 20px auto;
}

Any ideas?

Thanks