Invitations should be mailed 6-8 weeks prior to your wedding date for local weddings.
For destination weddings, mail them 10-12 weeks in advance.

All pieces should be arranged by size, with the smallest piece on top.
Slip the response card under the flap of the response envelope (be sure it has the proper postage stamp).
Insert everything into the mailing envelope with text side up.
The right hand side of the invitation should be closest to the envelope flap.

Take an assembled set to the post office to have it weighed and purchase adequate postage.
It would be terrible to have your invites returned, or your guests charged for insufficient postage!

Request your invitations be "hand cancelled" at the post office.
This reduces the risk of blemishing your envelopes and/or damaging any delicate contents.

Check to see if all the envelopes are securely closed.
It would be awful to have your invites come open and lost in the mail.