The default size for envelopes is Envelope #10.
In most printers, this size works fine. In some cases, we have found that this needs to be changed manually before printing by clicking File > Page Setup and choosing a different option for your paper size. -this will vary depending on your printer.
For some printers, it may be necessary to use Word to generate Envelopes using a pre-defined Word Template.
Click Tools > Options > File Locations to set this option.