Update
If I quit the Mac Mail program it will let me empty the trash. Does anybody know how to stop this from happening so I don't have to close the mail program everytime I want to empty the trash that has files in it I've emailed to somebody?
When you email an attachment it get's put into a temporary location, kind of like the temp folder in Windodws. So, when you delete the original file, you still have a "copy" of it somewhere else, or an active pointer to the original file. THe mail client is still using it so it can't be deleted.
It could be somewhat about how you are attaching the file. Does the file open int he email body after you attach it? If so, then it may be considered as open. So if you open a file in Preview, then delete the file without closing it out in preview, you can't empty the trash yet, because the file is still in use.
If this is the case, then maybe there is a way to attach it without it opening in the email body.
