wp_mail.headers.php

<?php
$to = "[email protected]";
$subject = "Learning how to send an Email in WordPress";
$content = "WordPress knowledge";
$headers = array(
	'Reply-To' => "Gustavo Bordoni <[email protected]>"
);

$status = wp_mail($to, $subject, $content, $headers);

wp_mail.html.php

<?php
$to = "[email protected]";
$subject = "Learning how to send an Email in WordPress";
$content = "WordPress <b>knowledge<b>";

add_filter( 'wp_mail_content_type', 'set_html_content_type' );

$status = wp_mail($to, $subject, $content);

// Reset content-type to avoid conflicts -- http://core.trac.wordpress.org/ticket/23578
remove_filter( 'wp_mail_content_type', 'set_html_content_type' );

function set_html_content_type() {
	return 'text/html';
}

wp_mail.multiple.php

<?php
$to = array(
	"Gustavo Bordoni <[email protected]>",
	"WordPress Developer <[email protected]>",
	"[email protected]"
);
$subject = "Learning how to send an Email in WordPress";
$content = "WordPress knowledge";

$status = wp_mail($to, $subject, $content);

wp_mail.simple.php

<?php
$to = "[email protected]";
$subject = "Learning how to send an Email in WordPress";
$content = "WordPress knowledge";

$status = wp_mail($to, $subject, $content);