How do I keep my envelopes from coming unglued in the mail?

Envelopes come open in transit when the seal is weak or the wrong adhesive warps the paper. A stronger, cleaner bond fixes it.

• Use a strong glue stick or double-sided tape along every flap seam for a firm, flat seal.
• Avoid liquid glue. It warps the paper and takes too long to set, leaving weak spots.
• Add a backup: a wax seal or a strip of washi tape over the closure flap adds security and looks intentional.
• Seal the corners and points, not just the center of the flap, since corners lift first.

Always test one sealed envelope before running the whole batch. Machine-sealed envelopes with a factory gum line avoid the problem altogether on larger orders.