I am applying the IPTC stationary pad (event, date, venue etc) when I save the images in PM. I then add the players names on the saved images using code replacement. Once the images are fully captioned I then e-mail them from PM via Mail. It's when the images are in Mail that the IPTC data has disappeared?
Maybe something that the Mail application in Leopard is doing when encoding the email is causing the problem. There are other issues in Leopard's version of Mail that we have tried to workaround so this could be just another issue that Apple needs to fix.
If you want to investigate this further, Photo Mechanic creates the email versions of the images in its cache folder. These images stick around until the next time you start up Photo Mechanic. You could copy them to a different folder and then browse them with Photo Mechanic to see if they have their IPTC data intact. If they don't have their IPTC data then the problem is in Photo Mechanic. If they do have their data intact then it is either a problem with Mail in Leopard, or it is a problem on the receiving end of the email attachments. If you BCC: yourself when sending photos, you should always receive the exact email that your regular recipient is receiving and you can investigate those images. If you find one that is missing its IPTC data then investigate the attachments cache.
On Mac OS X, Photo Mechanic's cache folder is located in the following path by default:
/Users/<your user name>/Library/Caches/Photo Mechanic/cache/
Inside the 'attachments' folder should be a numbered folder for each send photos session. Your photos will be in those folders. Copy them off to a different location and browse them with Photo Mechanic to see if they still retain your caption information. This will then let us know whether the problem originates withing Photo Mechanic or somewhere else.
HTH,
-Kirk