Signature image not appearing in sent email If I create a signature with mac mail and attach a png file to the signature, when I send the email the image appears as a black box on the sent email (examples attached).

In mac mail itself the image appears correctly.

How can I get the image to be sent correctly?
This is the right (and best) way to create an HTML signature that includes images:
http://matt.coneybeare.me/how-to-make-and-html-signature-in-apple-mail/