Email Services

📬 Jakarta Mail: Your Digital Post Office Adventure!

Imagine you have a magical post office right inside your computer. You can send letters to anyone in the world, receive letters from friends, and even attach photos and gifts! That’s exactly what Jakarta Mail does — but for emails!

🏠 What is Jakarta Mail?

Think of Jakarta Mail as your digital mailman. Just like how a mailman picks up your letters and delivers them to your friends, Jakarta Mail helps your Java programs send and receive emails.

Real-Life Example:

• When you order a pizza online and get a confirmation email → an app like Jakarta Mail sent it!
• When your school sends you a report card email → Jakarta Mail (or something like it) was behind the scenes!

graph TD
    A["Your Java App"] --> B["Jakarta Mail"]
    B --> C["📧 Email Server"]
    C --> D[📬 Friend's Inbox]

🔑 Mail Session: Your Post Office Membership Card

Before you can send letters, you need to register at the post office. The Mail Session is like your membership card — it tells the post office who you are and how to reach you.

What Does a Mail Session Store?

Example: Creating a Mail Session

Properties props = new Properties();
props.put("mail.smtp.host",
    "smtp.gmail.com");
props.put("mail.smtp.port", "587");
props.put("mail.smtp.auth", "true");

Session session = Session.getInstance(
    props,
    new Authenticator() {
        protected PasswordAuthentication
        getPasswordAuthentication() {
            return new PasswordAuthentication(
                "you@gmail.com", "secret");
        }
    }
);

Think of it like:

“Hi Post Office! I’m using Gmail’s office at door 587. Here’s my ID card!”

📜 MIME Messages: The Universal Letter Format

When you write a letter, you put it in an envelope with the address on top. MIME (Multipurpose Internet Mail Extensions) is the special envelope format that emails use.

Why MIME?

Regular letters can only have text. But MIME is like a magic envelope that can hold:

• 📝 Plain text
• 🎨 Fancy formatted text (HTML)
• 📷 Pictures
• 📎 Files
• 🎁 All of the above together!

Example: Creating a Simple MIME Message

MimeMessage message = new MimeMessage(session);

message.setFrom(
    new InternetAddress("me@example.com"));
message.setRecipient(
    Message.RecipientType.TO,
    new InternetAddress("friend@example.com"));
message.setSubject("Hello Friend!");
message.setText("How are you today?");

It’s like writing:

• From: Me
• To: My Friend
• Subject: Hello!
• Message: How are you?

📤 Sending Email: Dropping Your Letter in the Mailbox

Once your letter is ready, you need to send it! This is the exciting part — your message zooms through the internet to reach your friend!

The Magic Words to Send

Transport.send(message);

That’s it! One line and your email flies away! ✈️

Complete Sending Example

// 1. Set up your post office info
Properties props = new Properties();
props.put("mail.smtp.host", "smtp.gmail.com");
props.put("mail.smtp.port", "587");
props.put("mail.smtp.auth", "true");
props.put("mail.smtp.starttls.enable", "true");

// 2. Get your membership (session)
Session session = Session.getInstance(props,
    new Authenticator() {
        protected PasswordAuthentication
        getPasswordAuthentication() {
            return new PasswordAuthentication(
                "you@gmail.com", "yourpassword");
        }
    }
);

// 3. Write your letter
MimeMessage msg = new MimeMessage(session);
msg.setFrom(new InternetAddress("you@gmail.com"));
msg.setRecipient(Message.RecipientType.TO,
    new InternetAddress("friend@gmail.com"));
msg.setSubject("Greetings!");
msg.setText("Hope you have a great day!");

// 4. Send it!
Transport.send(msg);
System.out.println("Email sent! 🎉");

graph TD
    A["Write Message"] --> B["Connect to Server"]
    B --> C["Authenticate"]
    C --> D["Send Email"]
    D --> E["✅ Delivered!"]

📥 Receiving Email: Checking Your Mailbox

Now imagine you want to read the letters people sent you. You need to go to your mailbox and open it!

Two Ways to Check Mail

Example: Reading Emails with IMAP

Properties props = new Properties();
props.put("mail.store.protocol", "imaps");

Session session = Session.getInstance(props);

// Open your mailbox
Store store = session.getStore("imaps");
store.connect("imap.gmail.com",
    "you@gmail.com", "password");

// Go to inbox folder
Folder inbox = store.getFolder("INBOX");
inbox.open(Folder.READ_ONLY);

// Read all messages
Message[] messages = inbox.getMessages();
for (Message m : messages) {
    System.out.println("From: " +
        m.getFrom()[0]);
    System.out.println("Subject: " +
        m.getSubject());
}

// Close up
inbox.close(false);
store.close();

Think of it like:

1. 🔑 Unlock your mailbox
2. 📂 Open the inbox folder
3. 👀 Read each letter
4. 🔒 Lock it back up

📎 Email Attachments: Sending Gifts with Your Letters!

Sometimes you want to send more than just words. You want to send pictures, documents, or files. That’s what attachments are for!

How Attachments Work

Think of your email as a package with compartments:

• Compartment 1: Your text message
• Compartment 2: A photo
• Compartment 3: A PDF file

Each compartment is called a BodyPart, and they all go together in a Multipart container.

graph TD
    A["📦 Multipart Container"] --> B["📝 Text Part"]
    A --> C["📷 Image Part"]
    A --> D["📄 File Part"]

Example: Sending an Email with Attachment

MimeMessage message = new MimeMessage(session);
message.setFrom(new InternetAddress("me@mail.com"));
message.setRecipient(Message.RecipientType.TO,
    new InternetAddress("friend@mail.com"));
message.setSubject("Check out this photo!");

// Create the package (multipart)
Multipart multipart = new MimeMultipart();

// Add text compartment
MimeBodyPart textPart = new MimeBodyPart();
textPart.setText("Here's a cool picture!");
multipart.addBodyPart(textPart);

// Add file compartment
MimeBodyPart filePart = new MimeBodyPart();
filePart.attachFile(new File("photo.jpg"));
multipart.addBodyPart(filePart);

// Put package in envelope
message.setContent(multipart);

// Send it!
Transport.send(message);

Reading Attachments

When you receive an email with attachments, you need to unpack each compartment:

if (message.getContent()
    instanceof Multipart) {

    Multipart mp = (Multipart)
        message.getContent();

    for (int i = 0; i < mp.getCount(); i++) {
        BodyPart part = mp.getBodyPart(i);

        String fileName = part.getFileName();
        if (fileName != null) {
            // Save the attachment!
            part.saveFile("downloads/" + fileName);
            System.out.println("Saved: " + fileName);
        }
    }
}

🌟 Quick Summary: The Email Journey

graph TD
    A["📝 Write Message"] --> B["📧 Create MIME Message"]
    B --> C["🔑 Use Mail Session"]
    C --> D{What to do?}
    D -->|Send| E["📤 Transport.send"]
    D -->|Receive| F["📥 Store.getFolder"]
    E --> G["✅ Email Delivered!"]
    F --> H["📬 Read Messages"]

🎯 Remember These Key Players!

🚀 You Did It!

You now understand how emails work behind the scenes! Jakarta Mail is like having your own personal post office in your Java programs. You can:

• ✅ Set up your connection (Mail Session)
• ✅ Write emails (MIME Messages)
• ✅ Send them anywhere (Transport)
• ✅ Read incoming mail (Store & Folder)
• ✅ Attach files (Multipart)

You’re now an email wizard! 🧙‍♂️✨