I have created my mass email list just fine, but once it is sent I've noticed that each recipient gets 50 copies of the same letter. How do I get this program to send only one copy to each recipient?

That suggests there's something odd about your data source (e.g. 50 references to the same email address). The only reason I can see for that is if the data for each record differs, in which case the letters aren't really the same. if the data do differ, you can use Word's Catalogue/Directory Mailmerge facility (the terminology depends on the Word version). To see how to do so with any mailmerge data source supported by Word, check out my Microsoft Word Catalogue/Directory Mailmerge Tutorial at:
http://windowssecrets.com/forums/sho...merge-Tutorial
or:
http://www.gmayor.com/Zips/Catalogue%20Mailmerge.zip
The tutorial covers everything from list creation to the insertion & calculation of values in multi-record tables in letters. Do read the tutorial before trying to use the mailmerge document included with it.

Alternatively, you may want to try one of the Many-to-One Mail Merge add-ins, from:
Graham Mayor at http://www.gmayor.com/ManyToOne.htm; or
Doug Robbins at https://skydrive.live.com/?cid=5aedc...615E886B%21566

In addition to a 'Many to One' merge, the latter handles:
• Merge with Charts
• Duplex Merge
• Merge with FormFields
• Merge with Attachments
• Merge to Individual Documents
• Merge, Print and Staple

__________________
Cheers,
Paul Edstein
[Fmr MS MVP - Word]