I had the pleasure of creating an email for outlook 2010 based on sharepoint data. But when creating an outlook email, outlook in its wisdom reduces the image width and height to cm. Interestingly using the width and height kicks in correctly when you forward the email but not when you open it.
Hack Fix:
I had an image [720px X 150px] which should be [19.05cm X 3.98cm]. BUT outlook set the image width and height to [15.24cm X 3.18cm]. Clearly this is a problem.
The hack I used was setting the html image tag as follows:
<img src="...." style="width:720px; heigh:150px" width="900" height="187.5" />
Why that width and height?
Well it is the ratio (25% increase) between
(720 X 1.25 = 900)
and (150 X 1.25 = 187.5)
.Its not pretty but it works.