How to Send Mail to Custom Entity

Mscrm 3.0 user might facing an issue of sending mail to custom entity.which out of the box not supported.i also faced same situation at my client end .but after doing certain coding i achieve a solution for the same .we can easyly send mail to custom entity by using CRM Triggers(Callouts).if any one facing same issue can mail me for the code.my mail id is Sudhanshu2356@gmail.com.