I just received my invitations from Vistaprint and I think they came out beautiful, but I feel like the envelopes are super thin. Thin enough that I can see the design on the back of the invitation clearly through the front. I'm worried that once they're filled with all of the inserts and the belly bands, they're going to burst in the mail. For those of you who ordered and mailed invitations through Vistaprint, did the envelopes hold up? Did you buy thicker envelopes? I don't know if I'm overthinking this, but I don't want my invitations to fail to reach their recipients.