* mail: This is the base morpheme, the core meaning of the word. It refers to the system of sending letters and packages.
* -box: This is a suffix, added to the base morpheme "mail" to create a new word. It means a container for holding something.
* -es: This is a plural suffix, added to the base morpheme "mailbox" to indicate that there are more than one.
Therefore, the morphemes in the word "mailboxes" are mail, -box, and -es.