A: If your invitation and the event are fairly informal, you don't need one. But if you're planning a formal wedding, or even if you're sending several enclosures, inner envelopes are traditional, appropriate and practical. They keep all elements of the mailing neat and because typically only guests over 18 are listed on the outer envelope, inner envelopes also allow you to write which family members are being asked to the wedding (especially helpful when you aren't inviting kids).
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