The envelope containing a letter of introduction, should be addressed as follows:
NOTES OF CONGRATULATION OR CONDOLENCE.
Notes of congratulation and condolence should be brief, and the letter should only be sent by near and intimate friends. Do not allude to any subject except the one for which you are offering your congratulations or sympathy. Such notes should be made expressive of real feeling, and not be mere matters of form.
INVITATION TO A RECEPTION.
For a general reception, invitations are printed on cards. Their style is like the following, and do not require an answer unless "R.S.V.P." is upon one corner.
INVITATION TO A BALL.