Email was designed to mimic many aspects of postal mail. Electronic (thus the letter "e") mail is a way to send a message to a recipient, as is postal (or snail) mail. That message can consist of a letter, an advertisement, a bill, an announcement, a thank you, or a notification. It can include a photo or graphic of some kind. Either form of mail can be sent anonymously. Both have some regulations involved. Each can have multiple accounts (postal mail can through PO boxes or multiple physical addresses.) Both are better handled utilizing address books. Each type of mail must have a sender and a receiver. Both mail processes are sent through various routes that can change if necessary to get the message to the end user. Both types of messages are usually returned to the sender if the end address is incorrect. They both have established protocols. Snail mail and email have junk mail. Either service offers senders the option to request notification that the message has been received.
There are some differences between the two, of course. Email is much less costly than postal mail. Also, postal mail will never achieve the delivery of speed that email offers. On the flip side, there are places in the world that can receive postal mail but cannot receive an email, since those areas do not have internet service available.And one of the most obvious differences between email and postal mail: we cannot send something physical through email. We do not have Star Trek replicator processes figured out, yet! Maybe someday...