html email signatures - Embedding Images

I have created an html email signature for a client using absolute links to the images. When the email is received as long as the users email software allows image downloads the signature views correctly.

However my client has mentioned that when he receives the email via his blackberry instead viewing the image it displays the url path of the image.

I just assumed that the blackberry does not have the capability to view html signatures with images. However he has received an email from someone else and an image is shown in the email signature.

How can I do this?

Also is there a way of embedding images within an email signature so it does not have to reply of the users email software having image download option on?