In the Israeli company I work for, it has become common to use the verb 'stuff' for letters in an envelope, in company business writing. This usage sounds highly irregular to me (unless your trying to cram a stack of A4s into a small envelope), and I'm wondering whether it's an Israeli invention...

In case I'm correct in this assumption, does anyone know of an appropriate verb describing the action of simply putting a letter into an envelope?

Thank you!