Salesforce | Send email using apex code along with attachment and manage email history

1. Send simple email using apex :

Messaging.SingleEmailMessage emailTobeSent = new Messaging.SingleEmailMessage();
List <String> listEmailMembers = new List<String>();
listEmailMembers.add('email@domain.com');
emailTobeSent.setToAddresses(listEmailMembers);
emailTobeSent.setSubject('Hi, Just Testing');
emailTobeSent.setHtmlBody('msg : ' + msg);
Messaging.SendEmailResult [] r1 = Messaging.sendEmail(new Messaging.SingleEmailMessage[] {emailTobeSent}

2. Use template instead of manual Subject and body :

EmailTemplate et = [SELECT id,name  FROM EmailTemplate where Developername = :emailTemplate ];

Messaging.SingleEmailMessage emailTobeSent = new Messaging.SingleEmailMessage();
List <String> listEmailMembers = new List7lt;String>();
listEmailMembers.add('email@domain.com');
emailTobeSent.setToAddresses(listEmailMembers);
emailTobeSent.setTemplateId(et.id);
emailTobeSent.setTargetObjectId(UserInfo.getUserId());
Messaging.SendEmailResult [] r1 = Messaging.sendEmail(new messaging.SingleEmailMessage[] {emailTobeSent}

setTargetObjectId: Required if using a template, optional otherwise. The ID of the contact, lead, or user to which the email will be sent. The ID you specify sets the context and ensures that merge fields in the template contain the correct data.

3. Add attachment in email :

To add attachment in email Include following code :

Messaging.EmailFileAttachment attach = new Messaging.EmailFileAttachment();
attach.setContentType('application/pdf');
attach.setFileName('Myfile.pdf');
attach.setInline(false);
attach.Body = Blob.valueOf('Some Text');;
mail.setFileAttachments(new Messaging.EmailFileAttachment[] { attach });

4. Manage Email History under activity history of the object :

Messaging.SingleEmailMessage emailTobeSent = new Messaging.SingleEmailMessage();
List <String> listEmailMembers = new List<String>();
listEmailMembers.add('email@domain.com');
emailTobeSent.setToAddresses(listEmailMembers);
emailTobeSent.setTemplateId(et.id);
emailTobeSent.setTargetObjectId(ContactId);
emailTobeSent.saveAsActivity = true;
emailTobeSent.setWhatId(whatId)
 
Messaging.SendEmailResult [] r1 = Messaging.sendEmail(new messaging.SingleEmailMessage[] {emailTobeSent}