look at dbmail instead, you want to steer clear of xp_sendmail.
This feature will be removed in a future version of Microsoft SQL Server. Avoid using this feature in new development work, and plan to modify applications that currently use this feature. To send mail from SQL Server, use Database Mail.
but yeah you could just run a tsql job stop that uses dbmail.
http://msdn.microsoft.com/en-us/library/ms175887(v=sql.105).aspx