The script can automatically fill in the form using merge fields.
I have created my merge documents as a FM layout with database info automatically entered into merge fields. works very well and I have had no need to export to word for this.
I do not, however, have much experience using a mailing list but from what I've seen it looks pretty straitforward in FM
Hope this Helps
FileMaker is best when used as a database. MS Word is best used when used for word processing. Both have some features from the other camp and both can be used for generating form letters. So this isn't something I can make a straight forward recommendation on to you as it depends on what you need to accomplish.
As David583 indicates, FileMaker has a pretty complete set up for merging data in fields into a larger block of text. You can define a calculation field that merges the data or you can merge the data with merge fields on a layout. There are even ways where you can type a letter in a large text field, inserting "tags" that FileMaker can replace with text from other fields to create the customized form letters.
Here's another option:
You can export data from FileMaker as a merge file--a format specifically designed to support use with MS Word and you can then Import the merge file into MS Word for generating a series of form letters. I think there's now a way to do this with a direct link between Word and FileMaker without exporting/importing the data. Once you generated your letters, you can even store the completed letters, their PDFs, or their file references back in FileMaker container fields for future reference.