You can enable the mail merge option for custom records in NetSuite through these steps:
Navigate to Customization > Lists, Records, & Fields > Record Types.
Click on the Custom Record you want to edit.
Check the Enable Mail Merge box.
After enabling the mail merge option, you can use the mail merge feature to create personalized letters, bulk email messages, faxes, and mailing labels from your NetSuite data.
To add a note through suitelet:
var emaildata = {
body: field.fld_message + '
' + attachmentList + signature,// Add body here
author: sender.entityid,// Senders id
recipients: primary.email,// recipient id or email
subject: field.fld_subject,// Subject as string
cc: cc_entities,// Email id array or string
bcc: bcc_entities,// Email id array or string
relatedRecords: {
entityId: entities,// Specify the related record type
activityId: field.claimid,// Optional
}
};
email.send(emaildata);