Mailsave is a module that is designed to interact with mailhandler. It will detach files that are emailed to the site and save them with the node. It can also interact with other modules such as image, to provide functions like automatic conversion of nodes to image nodes. This can be used to allow posting of pictures from devices like mobile phones.
Mailsave for Drupal 6 released
The first official version of mailsave for Drupal 6 has been released, but at the moment it only includes the main mailsave module (the part that saves attachments) and the clean up filters.
The main extension module - mailsave_to_image - can't be released officially since the accompanying image module is only at alpha so is not yet fully stable. However, mailsave_to_image for Drupal 6 is available from HEAD and works with the current (alpha 2) release of image, so feel free to try it out.