Messaging.SingleEmailMessage mail = new Messaging.SingleEmailMessage();
// Strings to hold the email addresses to which you are sending the email.
String[] toAddresses = new String[] {'user@acme.com'};
String[] ccAddresses = new String[] {'smith@gmail.com'};
// Assign the addresses for the To and CC lists to the mail object.
mail.setToAddresses(toAddresses);
mail.setCcAddresses(ccAddresses);
// Specify the address used when the recipients reply to the email.
mail.setReplyTo('support@acme.com');
// Specify the name used as the display name.
mail.setSenderDisplayName('Salesforce Support');
// Specify the subject line for your email address.
mail.setSubject('New Case Created : ' + case.Id);
// Set to True if you want to BCC yourself on the email.
mail.setBccSender(false);
// Optionally append the salesforce.com email signature to the email.
// The email address of the user executing the Apex Code will be used.
mail.setUseSignature(false);
// Specify the text content of the email.
mail.setPlainTextBody('Your Case: ' + case.Id +' has been created');
mail.setHtmlBody('Your case:<b> ' + case.Id +' </b>has been created<p>'+
' View case <a href=https://prerelna1.pre.salesforce.com/'+case.Id+'>click here</a>');
// Send the email you have created.
Messaging.sendEmail(new Messaging.SingleEmailMessage[] { mail });