A Bug On Sqlserever

I'm using sql server extended store procedure xp_send mail to send mails from the sql server, at some places it loops i dont know where ant what makes it to loop, even if i type sql statement in the plsql window it sends approximately 512 mails but with different messages and subjects and i really dont know where it picks those details from, i'm totally lost. is this a bug on sql server. any info on this is apperciated, Thank you in advance.