Summary emails show oneboxed images in full size

It looks like there is a problem in how images are rendered in summary emails the summary includes a post with a onebox which includes an image. From what I can see, these images are displayed in their original size (i.e. the dimensions of the image on the original website).

When displayed in the onebox on the forum, the size is adjusted to the size of the onebox but this size adjustment does not seem to make it into the summary email.