Thank you for your post.
I'm running FileMaker Pro 10.0v3 on an iMac with Mac OS X 10.5.8. I do not have access to a Tiger (10.4.x) machine at this time.
My default mail program is Apple Mail, and I do not have Entourage.
I have 100 contacts in the Email Campaign Management sample file, and when I send emails via the campaign, all 100 emails are sent.
In the "Send Campaign" script, I would temporarily enter a "Halt Script" script step just prior to the Send Mail command (near the bottom). When the script halts, look at the values in the various fields, including Campaigns::g_Contact List_Temp, where there will be many lines of text that, in your case, should now be 56 separate lines. Since this loop is not stopping, somehow the g_Contacts List_Temp is never becoming empty.
Let me know if you are still having difficulty.
Thanks for the response and apologies for taking so long to reply - we had a baby over Xmas and life rather hectic. I recently treated myself to a copy of Prosser & Coffey's Filemaker Pro 10: The missing manual and with that have set up my own DB and am now emailing from that successfully. When I get a mo I will go back to the original file and do what you suggest, just to find out what was going wrong.