libreoffice.org Free!

But, downloading and figuring out the whole mess might be a little much. It is, though, an extraordinarily worthwhile package if you need anything in there. It includes, as it should, mailmerge.

WordPerfect is another one, but it costs money.

Word does have the ability, if you have Word.

The winner might be Wordpad, also free, which is probably already on your computer (if windows). https://www.bing.com/search?q=envelope+printing+template+in+wordpad&cvid=86734f0d3e154b2bb0a82d65407f1c04&aqs=edge.1.0l4.12577j0j1&pglt=43&FORM=ANNTA1&PC=U531

Avery.com used to put out a downloadable app that was absolutely the best for printing labels, envelopes and other stuff, but it apparently made them no money so they killed it.

I did a search for "envelope template" and all sorts of good stuff showed up, including a few that gave you PDF templates for dozens of sizes.

Thanks. I'll check it out