i keep getting e-mails from Mailer Daemon

[LilSeXyGrNeyes]

Hi.............keep getting e-mails from a MAILER DAEMON, sayin that an e-mail that i sent out didnt go through, i looked in my mail sent box and it was full of Sent mail with a subject i never heard of sent to over 40 people..............i never sent these e-mails, i want it to stop and i dont how to make it stop, so if u could help me it would be greatfully appreciated                                                                                                                          Thank You                                                                        Erica Keresey