A family of Microsoft word processing software products for creating web, email, and print documents.
In that case, the first step should be to ensure Office is working correctly (e.g. by repairing the Office installation via Start > Windows Control Panel > Programs > Programs & Features > Microsoft Office (version) > Change > Repair). The next step would be to merge to a document instead of to email, with the email address field in the mailmerge, and confirm that all the expected data are present. So far, I see no indication that either of these has been done.