Refined to include the ifplugin directive (which if you prefer can go
after the three mimeheader lines).
ifplugin Mail::SpamAssassin::Plugin::ImageInfo
mimeheader __MIME_GIF Content-Type =~ /image\/gif/i
mimeheader __MIME_PNG Content-Type =~ /image\/png/i
mimeheader __MIME_JPEG Content-Type =~ /image\/jpe?g/i
body __GIF_ATTACH eval:image_count('gif',1)
body __PNG_ATTACH eval:image_count('png',1)
body __JPEG_ATTACH eval:image_count('jpeg',1)
meta IMAGE_MISMATCH (__MIME_GIF && !__GIF_ATTACH) || (__MIME_PNG &&
!__PNG_ATTACH) || (__MIME_JPEG && !__JPEG_ATTACH)
describe IMAGE_MISMATCH Contains wrong image format for MIME header
score IMAGE_MISMATCH 1.0
endif
