text: why is it that an e-mail would take a day to come back " mailer daemon "? seems that usually if there is an error in the address one types, a " mailer daemon" message comes back almost immediately. what possibly could cause it to take a " day " plus / minus to return ? appreciate a knowlegeable answer. the mailer deamon is the name of the program on your email providers server that is trying to send out the mail. what it's doing is trying over and over again to send out the mail. it doesn't stop when it fails the first time because it doesn't know if the server that would accept the mail is just temporarily unavailable, rather than non-existent.