method
mineral
manhunt
minivan
mustard
name start with M and ends with D ,seven letters
Mexico.
Macaw
· muffin
Maracas starts with m. a mandolin
mininova
millet
mammoth
Macao
marjoram
Pendulum
The answer to the riddle is "Mailbox." It starts with the letter 'M,' ends with 'X,' and can contain an endless number of letters (as in mail) inside it.