I am using Amazon EC2 Instance for one of my project, I have installed LAMP on linux server and now while I am trying to send email using simple function it is not sending email
Although your problem relates to Sendmail have you tried following Amazons Documentation?
http://docs.aws.amazon.com/ses/latest/DeveloperGuide/send-email-smtp-app.html
This uses postfix but it seems like a better alternative and there's help readily available for it.
You also can use SMTP as Amazon SES supports this:
http://docs.aws.amazon.com/ses/latest/DeveloperGuide/send-email-smtp.html
I know this doesn't directly answer your question. You might just need to configure the mail
settings in php.ini
.