Merge templates used in mail merges have a number of advantages over mail merges using the Letter Wizard, and one major disadvantage:
Mail merges using merge templates can be sent to more than one recipient.
Merge templates can be saved for reuse in later mail merges. Once a merge template is designed and saved, it can be used with the same or different set of recipients as the original mail merge.
Merge templates can use Outlook fields that aren't available in documents produced by the Letter Wizard, such as fax numbers and alternate mailing addresses.
It's much easier to control the placement of merge fields in a document than it is to control where information or text inserted by the Letter Wizard is placed. ...