Does anyone have good tips for mailing cakes?

I started making persimmon pudding today (traditional steamed cakes) with the intention of mailing them to several friends on the other side of the country. And then I started to worry about the logistics....

They resemble cake, so I don't think there's any harm they could make someone sick after a few days in the mail, but how should I package them to keep them from drying out? Would adding a glaze help to retain moisture, or just soak in and make it all a mushy mess? How fast is the mail running this time of year (in the U.S.), anyway?

Any tips are greatly appreciated!