During the 19th century, invitations were mailed two weeks before the wedding in double envelopes. Postal systems were still in their infancy and posted letters often got dirty and marked up en route. The outer envelope, containing the recipients’ address (along with the required postage), was removed by a servant and a clean, presentable inner envelope was presented to the master of the house.
Your mail may not be delivered the same today, yet the inner envelope continues to serve a purpose. It will let your guest know exactly who is or isn’t (by omission) invited to the wedding. The outer envelope may say “Mr. and Mrs. Thomas A. Ford,” the inner envelope (which uses a less formal form of address) will read, “Mr. and Mrs. Ford / Jack and Jane [another option: Jack Ford / Jane Ford],” indicating that the Ford’s kids are also invited. If the Ford’s had other children not listed, perhaps their youngest child(ren), it would mean that only the older ones were invited to attend. If Mr. and Mrs. Ford’s names appeared on the inner envelope alone, then none of their kids are invited.
The use of the inner envelope also offers you a gracious way to indicate that your guest may bring a plus-one, with either a name included or written as “and Guest” if the name isn’t known.
If you choose not to go with the inner envelope, you will want to clearly state who is invited to the wedding on the mailing envelope. Follow the same rule as with the inner envelope and write out who is to attend. In the case above, you would write Mr. and Mrs. Ford / Jack and Jane or write “and family” for a more informal approach.
It would look something like this:
Mr. and Mrs. Ford
Jack and Jane
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