Posters are cheap to send and easy to ruin, and the delivery choice follows the state the sheet is already in.
Rolled sheets
A rigid tube, wide enough that the roll is not squeezed, caps taped, with an outer wrap because tube ends get crushed in sorting.
Tubes are light but long, and length can attract a surcharge. Check before you quote. How delivery is charged.
Folded sheets
Flat, between boards, in a rigid flat box. Never flatten a folded poster to make it ship better — that is restoration and it is the buyer's decision. Packing posters.
Framed pieces
Do not post glass. Collection, or sell it unframed.
When collection is the honest answer
For large sheets, for anything framed, and for anything where the paper is already fragile. Pickup terms are agreed before bidding with a collect-by window of 72 hours unless you set otherwise. How pickup works.
Combining wins
Several rolled posters go in one tube comfortably, interleaved, which makes combining genuinely valuable here. It is on by default and you set what each later win adds.
Folded sheets combine in one flat box just as well. Mixing the two does not — say which you are sending.
Questions people ask
Can I post a poster in a soft mailing tube?
No. Rigid, with taped caps.
Does the monsoon matter for paper?
More than anything else. Moisture barrier inside the tube or box, always.
Should lobby cards ship separately?
They can go in the flat box with a folded sheet, boarded.