image_tag resolution of path to image not working in html emails

I'm using the inline_attachment gem at:

to include images in my html emails and almost have everything working
well now, except that what works in development does not work in

when sent from the development machine here's what gets inserted by
image_tag in the email that goes out:

<img alt="" height="35px" src="cid:
1237146569.011RedeyeLogo.gif@inline_attachment" style="border: none;"
width="234px" />

when sent from production:

<img alt="" height="35px"
src="/images/RedeyeLogo.gif?1236723122" style="border: none;"
width="234px" />

Note the relative path.

So, something's not getting resolved correctly in production. Can
anyone pt me in the right direction to figure out why?