your are assigning
string fromEmailid = "";
if (Email_NO == 1)
fromEmailid = "vk@gmail.com";
else if (Email_NO == 2)
fromEmailid ="rk@gmail.com";
else
fromEmailid ="";
but where are you using this?
see if u gonna pass different email id for diffrent users then there must be specific conditions for them, if u write inline conditions, then it means your code is not generic.
U need to have a unique id for sending two mails
Add a column FromEmailIdConfigruation column in db or grid:
Name EmailId FromEmailId
Rakesh Rakesh@gmail.com rk@gmail.com
then use this from email id in your code.