Postal & Email - Similarities & Dissimilarities

In class, we have discussed about some of the similarities between postal service and emails. We found out about twenty five of them, along with some differences. Here are some of them.
Similarities:

• Both requires a sender and a receiver. 
• Both have many stops along their traveling routes.
• Both need addresses to send to.
• Both can send bulk mails.
• Come in various sizes.
• Both can send letters.
• Have established protocol.
• Both can be bounced.
• Both have a mail box

Differences:

• Postal requires stamp, but emails don't
• Postal requires long time to get through, emails get through almost instantly
• Postal is physical, while email is digital

There wasn't much differences between them but the big and obvious fact that one is physical mails and one is digital mails still remains.
But in some distant future, maybe humans will be able to send physical mails over the net with some kind of warping device. The possibility is there, and I am excited when I think of it.