There are certain guidelines on how to address wedding invitations inner envelopes. It used to be traditional for invitations to be mailed with two envelopes – an inner envelope & an outer envelope. With the advent of more modern wedding invitations including pocket styles, double envelopes are not always included.
If your chosen design includes two envelopes, the inner envelope is the smaller of the two and the one that has the colored lining option for a nominal charge. It holds your wedding invitation along with any enclosure cards and is then inserted into the outer envelope for mailing but before this happens both envelopes need to be hand addressed.
Please use this link to read the specific guidelines for how to address wedding invitations inner envelopes.