Vertical envelope A4 mockup. Template paper letter, folder. White blank letter envelopes C4, a3, a5 size. Open vertical, closed envelope mockup for mail. Set paper envelope of front, back side. vector. Vertical envelope A4 mockup. Template paper letter, folder. White blank letter envelopes C4, a3, a5 size. Open vertical, closed envelope mockup for mail. Set paper envelope front, back side. vector