Invitation question

After looking over my envelopes for my invites today, I realized that only my inner envelope has a lining. Is that the way it is supposed to be or are both inner and outter envelopes supposed to have the lining?

Thanks Teri. I just noticed it last night.

Please forgive me if I translate the meaning behind this incorrectly, but I heard this a while back regarding invitations. During times of horses instead of cars, the outer envelopes with the addresses were destroyed or stained from the dirt roads, so the inner envelope was used in order to protect the invitation and allowed it to be maintained for an elegant presentation. That is also why the inner envelope gets the lining. So there are those brides who now decide to skip the inner envelope entirely, although many still stick with this tradition of 2 envelopes. When a bride posted this a while back, I thought it was an interesting bit of trivia! I hope I've written it correctly here! Good luck!