I have created a Map/Reduce script in sandbox which I am sending an email to the customer, but the email is not being sent.

Hi Vishal, did you check your sandbox e-mail settings? NetSuite Applications Suite - Setting Preferences for Sandbox Email

@Sanne Yes, Email sending to logging user. from suitelet its work but not from Map/reduce. And in email sent log status is Not Sent

Does it work if you change the setting from 'Send Email to Logged in User' to 'Send Email to (specific e-mailaddress)'? Maybe there is no login context in M/R scripts and that's causing the issue.

Thanks @Sanne It worked after changing the setting from 'Send Email to Logged-in User' to 'Send Email to'. If I deploy it to production, it will work as expected and send the email to the customer, right?

In the mails that are triggered in the Sandbox environment, a line in the mail subject will say it was meant for X (customer e-mail). If that looks okay, then it should work as expected in production.

Okay Thanks @Sanne

You need to send configuration in Email Preferences

Maybe there is no login context in M/R scripts and that's causing the issue.

This is correct. There is no logged-in user in a Map/Reduce script.