Depends what you mean. Typically, when you are merging to printer or a new
document, Word uses the fonts you have specified in your mail merge main
document. If you have inserted fields without any \*Charformat or
\*Mergeformat switches (and typically, but not necessarily, if you have left
in the default \*Mergeformat switches) Word will output the field data using
the font of the surrounding text.
If you are merging to e-mail then the same should be true if you are using
merge to an attachment or HTML (although the appearance of the latter will
depend to some extent on the recipient's system). If you are merging to
"plan text" then your e-mail is sent without any font information and is
completely dependent on how the recipient's e-mail software displays plain
text.
