It depends on the plant and where you are sending it to. We received the rhododendrons from Glendoick yesterday they were lifted from the ground but had a soil ball around them which was in a plastic bag. The tops had been partially cut back and tied together with twine and they arrived in a box which they fitted into without packaging. Sending small plants we tend to put the whole thing in a container of some sort that is the right size then into a padded bag and off it goes.

hi thanks moon grower

I also pop them in plastic bag with a little soil , or wrapped in damp kitchen paper. then in a suitable box/padded envelop and off to the post office.
If they have grown in a pot I tend to remove the pot just to lighten the cost.

I cut tall foliage down again to reduce cost but also to help the plant cope.

thanks seaburngirl