Bottom of JScrollPane is cut off

FlowLayout doesn't "wrap" well. Consider a different layout, GridBagLayout for example...

Also, stop "trying" to force a size onto your UI, you don't have enough control over the factors which affect sizing to do this.

Instead, rely on the layout managers and API functionality. For example, instead of calling setSize on your frame, call pack...I would have posted soon, but it took me this long to find that call...I was scratching my head wondering why the UI wouldn't layout the way I expected...

import java.awt.Color;
import java.awt.EventQueue;
import java.awt.Font;
import java.awt.GridBagConstraints;
import java.awt.GridBagLayout;
import java.awt.Insets;
import javax.swing.JFrame;
import static javax.swing.JFrame.EXIT_ON_CLOSE;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.border.LineBorder;

public class Test extends JFrame {

    public static void main(String[] args) {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
                }

                Test frame = new Test("Testing", 400, 400);
            }
        });
    }

    Test(String title, int x, int y) {

        super(title);
        setDefaultCloseOperation(EXIT_ON_CLOSE);
        addElements();
        pack();
        setVisible(true);
//        setResizable(false);

    }

    public void addElements() {

        Font size30 = new Font(null, Font.PLAIN, 30);

        //--- User Info ---//
        JPanel userInfo = new JPanel(new GridBagLayout());

        GridBagConstraints gbc = new GridBagConstraints();
        gbc.insets = new Insets(2, 2, 4, 2);
        gbc.gridx = 0;
        gbc.gridy = 0;
        JLabel userLabel = new JLabel("Username: ");
        JTextField userField = new JTextField(12);
        userInfo.add(userLabel, gbc);
        gbc.gridx++;
        userInfo.add(userField, gbc);

        JLabel passLabel = new JLabel("Password: ");
        JTextField passField = new JTextField(10);
        gbc.gridx++;
        userInfo.add(passLabel, gbc);
        gbc.gridx++;
        userInfo.add(passField, gbc);

        JLabel serverLabel = new JLabel("Mail Server: ");
        JTextField serverField = new JTextField(10);
        gbc.gridx++;
        userInfo.add(serverLabel, gbc);
        gbc.gridx++;
        userInfo.add(serverField, gbc);

        JLabel portLabel = new JLabel("Server Port: ");
        JTextField portField = new JTextField(3);
        gbc.gridx++;
        userInfo.add(portLabel, gbc);
        gbc.gridx++;
        userInfo.add(portField, gbc);

        gbc = new GridBagConstraints();
        gbc.insets = new Insets(2, 2, 4, 2);
        gbc.gridx = 0;
        gbc.gridy = 0;
        //--- To: CC: and Subject Fields ---//
        JPanel msgInfo = new JPanel(new GridBagLayout());

        JLabel toLabel = new JLabel("To: ");
        JTextField toField = new JTextField(30);
        msgInfo.add(toLabel, gbc);
        gbc.gridx++;
        msgInfo.add(toField, gbc);

        JLabel subLabel = new JLabel("Subject: ");
        JTextField subField = new JTextField(30);
        gbc.gridx++;
        msgInfo.add(subLabel, gbc);
        gbc.gridx++;
        msgInfo.add(subField, gbc);

        //--- Body ---//
//        JPanel bodyPnl = new JPanel(new GridBagLayout());
//        gbc = new GridBagConstraints();
//        gbc.insets = new Insets(2, 2, 4, 2);
//        gbc.gridx = 0;
//        gbc.gridy = 0;

        JLabel bodyLabel = new JLabel("Body");
        bodyLabel.setHorizontalAlignment(JLabel.CENTER);
        bodyLabel.setFont(size30);

        JTextArea bodyField = new JTextArea(30, 70);
        bodyField.setLineWrap(true);
        bodyField.setWrapStyleWord(true);

        JScrollPane bodyScroll = new JScrollPane(bodyField);

        bodyScroll.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_AS_NEEDED);
//        bodyScroll.setBounds(getX(), getY(), bodyField.getWidth(), bodyField.getHeight());

        setLayout(new GridBagLayout());
        gbc = new GridBagConstraints();
        gbc.gridx = 0;
        gbc.gridy = 0;
        gbc.weightx = 1;
        gbc.fill = GridBagConstraints.HORIZONTAL;

        add(userInfo, gbc);
        gbc.gridy++;
        add(msgInfo, gbc);
        gbc.gridy++;
        gbc.insets = new Insets(10, 10, 4, 10);
        add(bodyLabel, gbc);
        gbc.gridy++;
        gbc.insets = new Insets(4, 10, 10, 10);
        gbc.weighty = 1;
        gbc.fill = GridBagConstraints.BOTH;
        add(bodyScroll, gbc);

    }

}