Do you have the Simply Scoring tool from Stampin Up? It's the best new tool to come along in a long time. It make scoring so easy. Especially if you have a lot of scoring to do. And now there's a diagonal plate that fits on top of the Simply Scoring Tool. It makes envelope so easy to do that everyone should have it. Just think about making envelopes to match your cards. Or make beautiful envelopes out of DSP like the one below on the top right. As long as the post office can read the address you're okay. It's kind of hard to see but there's a label on this envelope. And if you don't want the whole envelop out of DSP then just cut some to line the inside of the flap like the one on the top left.
Here's the other side of the envelope made with DSP. Isn't this just the neatest thing you've ever seen? I can see wedding invitations made with matching envelopes, Christmas cards with red or green envelopes or just pretty note cards and envelopes.