Hi krishnakant1974,
Welcome to LQ!!!
I would like to mention that the question that you have posted is very vague. What exactly you want to know about sendmail and postfix configuration? If you are looking for "HowTo" then it will be a good idea to type the same string array in Google's search box and you will get many links on the same.
Here is the link that will help you to frame your questions in better manner in future:
https://www.linuxquestions.org/linux...Ask_a_Question