Index: src/wp-admin/includes/schema.php
===================================================================
--- src/wp-admin/includes/schema.php	(revision 33712)
+++ src/wp-admin/includes/schema.php	(working copy)
@@ -393,10 +393,6 @@
 	'comments_notify' => 1,
 	'posts_per_rss' => 10,
 	'rss_use_excerpt' => 0,
-	'mailserver_url' => 'mail.example.com',
-	'mailserver_login' => 'login@example.com',
-	'mailserver_pass' => 'password',
-	'mailserver_port' => 110,
 	'default_category' => 1,
 	'default_comment_status' => 'open',
 	'default_ping_status' => 'open',
@@ -499,6 +495,9 @@
 
 	// 4.3.0
 	'finished_splitting_shared_terms' => 1,
+
+	// 4.4
+	'post_by_email_enabled' => 0,
 	);
 
 	// 3.3
Index: src/wp-admin/includes/upgrade.php
===================================================================
--- src/wp-admin/includes/upgrade.php	(revision 33712)
+++ src/wp-admin/includes/upgrade.php	(working copy)
@@ -540,6 +540,8 @@
 
 	maybe_disable_link_manager();
 
+	maybe_disable_post_by_email();
+
 	maybe_disable_automattic_widgets();
 
 	update_option( 'db_version', $wp_db_version );
@@ -1599,6 +1601,19 @@
 }
 
 /**
+ * Executes changes made in WordPress 4.4.0
+ *
+ * @since 4.4.0
+ */
+function upgrade_440() {
+	global $wp_current_db_version;
+	if ( $wp_current_db_version < 33056 && 'mail.example.com' !== get_option( 'mailserver_url' ) ) {
+		// Previously set to 0 by populate_options()
+		update_option( 'post_by_email_enabled', 1 );
+	}
+}
+
+/**
  * Executes network-level upgrade routines.
  *
  * @since 3.0.0
@@ -2562,6 +2577,21 @@
 }
 
 /**
+ * Disables Post by Email options if, at the time of upgrade, the settings have not been changed from original defaults.
+ *
+ * @since 4.4.0
+ *
+ * @global int  $wp_current_db_version
+ */
+function maybe_disable_post_by_email() {
+	global $wp_current_db_version;
+
+	if ( $wp_current_db_version > 33056 && 'mail.example.com' === get_option( 'mailserver_url' ) ) {
+		update_option( 'post_by_email_enabled', 0 );
+	}
+}
+
+/**
  * Runs before the schema is upgraded.
  *
  * @since 2.9.0
Index: src/wp-admin/options-writing.php
===================================================================
--- src/wp-admin/options-writing.php	(revision 33712)
+++ src/wp-admin/options-writing.php	(working copy)
@@ -22,15 +22,6 @@
 		'<p>' . __('You must click the Save Changes button at the bottom of the screen for new settings to take effect.') . '</p>',
 ) );
 
-/** This filter is documented in wp-admin/options.php */
-if ( apply_filters( 'enable_post_by_email_configuration', true ) ) {
-	get_current_screen()->add_help_tab( array(
-		'id'      => 'options-postemail',
-		'title'   => __( 'Post Via Email' ),
-		'content' => '<p>' . __( 'Post via email settings allow you to send your WordPress install an email with the content of your post. You must set up a secret e-mail account with POP3 access to use this, and any mail received at this address will be posted, so it&#8217;s a good idea to keep this address very secret.' ) . '</p>',
-	) );
-}
-
 /** This filter is documented in wp-admin/options-writing.php */
 if ( apply_filters( 'enable_update_services_configuration', true ) ) {
 	get_current_screen()->add_help_tab( array(
@@ -108,45 +99,10 @@
 do_settings_fields('writing', 'remote_publishing'); // A deprecated section.
 ?>
 </table>
-
+<?php if ( get_option( 'post_by_email_enabled' ) && apply_filters( 'enable_post_by_email_configuration', true ) ) { ?>
+<h3 class="title"><?php _e( 'Post via e-mail' ) ?></h3>
+<p><?php _e( 'This functionality is no longer packaged with WordPress.  To continue using it, please install the <a href="http://wordpress.org/plugins/post-by-email">Post By Email plugin</a>.' ); ?></p>
 <?php
-/** This filter is documented in wp-admin/options.php */
-if ( apply_filters( 'enable_post_by_email_configuration', true ) ) {
-?>
-<h3 class="title"><?php _e('Post via e-mail') ?></h3>
-<p><?php printf(__('To post to WordPress by e-mail you must set up a secret e-mail account with POP3 access. Any mail received at this address will be posted, so it&#8217;s a good idea to keep this address very secret. Here are three random strings you could use: <kbd>%s</kbd>, <kbd>%s</kbd>, <kbd>%s</kbd>.'), wp_generate_password(8, false), wp_generate_password(8, false), wp_generate_password(8, false)) ?></p>
-
-<table class="form-table">
-<tr>
-<th scope="row"><label for="mailserver_url"><?php _e('Mail Server') ?></label></th>
-<td><input name="mailserver_url" type="text" id="mailserver_url" value="<?php form_option('mailserver_url'); ?>" class="regular-text code" />
-<label for="mailserver_port"><?php _e('Port') ?></label>
-<input name="mailserver_port" type="text" id="mailserver_port" value="<?php form_option('mailserver_port'); ?>" class="small-text" />
-</td>
-</tr>
-<tr>
-<th scope="row"><label for="mailserver_login"><?php _e('Login Name') ?></label></th>
-<td><input name="mailserver_login" type="text" id="mailserver_login" value="<?php form_option('mailserver_login'); ?>" class="regular-text ltr" /></td>
-</tr>
-<tr>
-<th scope="row"><label for="mailserver_pass"><?php _e('Password') ?></label></th>
-<td>
-<input name="mailserver_pass" type="text" id="mailserver_pass" value="<?php form_option('mailserver_pass'); ?>" class="regular-text ltr" />
-</td>
-</tr>
-<tr>
-<th scope="row"><label for="default_email_category"><?php _e('Default Mail Category') ?></label></th>
-<td>
-<?php
-wp_dropdown_categories(array('hide_empty' => 0, 'name' => 'default_email_category', 'orderby' => 'name', 'selected' => get_option('default_email_category'), 'hierarchical' => true));
-?>
-</td>
-</tr>
-<?php do_settings_fields('writing', 'post_via_email'); ?>
-</table>
-<?php } ?>
-
-<?php
 /**
  * Filter whether to enable the Update Services section in the Writing settings screen.
  *
Index: src/wp-includes/default-filters.php
===================================================================
--- src/wp-includes/default-filters.php	(revision 33712)
+++ src/wp-includes/default-filters.php	(working copy)
@@ -309,6 +309,8 @@
 
 // If the upgrade hasn't run yet, assume link manager is used.
 add_filter( 'default_option_link_manager_enabled', '__return_true' );
+// If the upgrade hasn't run yet, assume the post by mail options are set.
+add_filter( 'default_option_post_by_email_enabled', '__return_true' );
 
 // This option no longer exists; tell plugins we always support auto-embedding.
 add_filter( 'default_option_embed_autourls', '__return_true' );
Index: src/wp-includes/formatting.php
===================================================================
--- src/wp-includes/formatting.php	(revision 33712)
+++ src/wp-includes/formatting.php	(working copy)
@@ -3526,7 +3526,6 @@
 		case 'medium_size_h':
 		case 'large_size_w':
 		case 'large_size_h':
-		case 'mailserver_port':
 		case 'comment_max_links':
 		case 'page_on_front':
 		case 'page_for_posts':
@@ -3584,9 +3583,6 @@
 
 		case 'date_format':
 		case 'time_format':
-		case 'mailserver_url':
-		case 'mailserver_login':
-		case 'mailserver_pass':
 		case 'upload_path':
 			$value = $wpdb->strip_invalid_text_for_column( $wpdb->options, 'option_value', $value );
 			if ( is_wp_error( $value ) ) {
Index: src/wp-mail.php
===================================================================
--- src/wp-mail.php	(revision 33712)
+++ src/wp-mail.php	(working copy)
@@ -1,9 +1,14 @@
 <?php
 /**
- * Gets the email message from the user's mailbox to add as
- * a WordPress post. Mailbox connection information must be
- * configured under Settings > Writing
+ * This file is deprecated and has been replaced by the
+ * plugin Post By Email.  Instead of loading wp-mail.php to
+ * trigger the "wp-mail.php" action, you should trigger it
+ * yourself, either in a plugin/theme hook or via wp_cron.
  *
+ * For more information:
+ * http://wordpress.org/plugins/post-by-email/
+ * http://codex.wordpress.org/Category:WP-Cron_Functions
+ *
  * @package WordPress
  */
 
@@ -10,9 +15,7 @@
 /** Make sure that the WordPress bootstrap has run before continuing. */
 require(dirname(__FILE__) . '/wp-load.php');
 
-/** This filter is documented in wp-admin/options.php */
-if ( ! apply_filters( 'enable_post_by_email_configuration', true ) )
-	wp_die( __( 'This action has been disabled by the administrator.' ) );
+_deprecated_file( basename( __FILE__ ), '4.4.0', 'wp-mail.php' );
 
 /**
  * Fires to allow a plugin to do a complete takeover of Post by Email.
@@ -20,241 +23,3 @@
  * @since 2.9.0
  */
 do_action( 'wp-mail.php' );
-
-/** Get the POP3 class with which to access the mailbox. */
-require_once( ABSPATH . WPINC . '/class-pop3.php' );
-
-/** Only check at this interval for new messages. */
-if ( !defined('WP_MAIL_INTERVAL') )
-	define('WP_MAIL_INTERVAL', 300); // 5 minutes
-
-$last_checked = get_transient('mailserver_last_checked');
-
-if ( $last_checked )
-	wp_die(__('Slow down cowboy, no need to check for new mails so often!'));
-
-set_transient('mailserver_last_checked', true, WP_MAIL_INTERVAL);
-
-$time_difference = get_option('gmt_offset') * HOUR_IN_SECONDS;
-
-$phone_delim = '::';
-
-$pop3 = new POP3();
-
-if ( !$pop3->connect( get_option('mailserver_url'), get_option('mailserver_port') ) || !$pop3->user( get_option('mailserver_login') ) )
-	wp_die( esc_html( $pop3->ERROR ) );
-
-$count = $pop3->pass( get_option('mailserver_pass') );
-
-if( false === $count )
-	wp_die( esc_html( $pop3->ERROR ) );
-
-if( 0 === $count ) {
-	$pop3->quit();
-	wp_die( __('There doesn&#8217;t seem to be any new mail.') );
-}
-
-for ( $i = 1; $i <= $count; $i++ ) {
-
-	$message = $pop3->get($i);
-
-	$bodysignal = false;
-	$boundary = '';
-	$charset = '';
-	$content = '';
-	$content_type = '';
-	$content_transfer_encoding = '';
-	$post_author = 1;
-	$author_found = false;
-	$dmonths = array('Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec');
-	foreach ($message as $line) {
-		// Body signal.
-		if ( strlen($line) < 3 )
-			$bodysignal = true;
-		if ( $bodysignal ) {
-			$content .= $line;
-		} else {
-			if ( preg_match('/Content-Type: /i', $line) ) {
-				$content_type = trim($line);
-				$content_type = substr($content_type, 14, strlen($content_type) - 14);
-				$content_type = explode(';', $content_type);
-				if ( ! empty( $content_type[1] ) ) {
-					$charset = explode('=', $content_type[1]);
-					$charset = ( ! empty( $charset[1] ) ) ? trim($charset[1]) : '';
-				}
-				$content_type = $content_type[0];
-			}
-			if ( preg_match('/Content-Transfer-Encoding: /i', $line) ) {
-				$content_transfer_encoding = trim($line);
-				$content_transfer_encoding = substr($content_transfer_encoding, 27, strlen($content_transfer_encoding) - 27);
-				$content_transfer_encoding = explode(';', $content_transfer_encoding);
-				$content_transfer_encoding = $content_transfer_encoding[0];
-			}
-			if ( ( $content_type == 'multipart/alternative' ) && ( false !== strpos($line, 'boundary="') ) && ( '' == $boundary ) ) {
-				$boundary = trim($line);
-				$boundary = explode('"', $boundary);
-				$boundary = $boundary[1];
-			}
-			if (preg_match('/Subject: /i', $line)) {
-				$subject = trim($line);
-				$subject = substr($subject, 9, strlen($subject) - 9);
-				// Captures any text in the subject before $phone_delim as the subject
-				if ( function_exists('iconv_mime_decode') ) {
-					$subject = iconv_mime_decode($subject, 2, get_option('blog_charset'));
-				} else {
-					$subject = wp_iso_descrambler($subject);
-				}
-				$subject = explode($phone_delim, $subject);
-				$subject = $subject[0];
-			}
-
-			/*
-			 * Set the author using the email address (From or Reply-To, the last used)
-			 * otherwise use the site admin.
-			 */
-			if ( ! $author_found && preg_match( '/^(From|Reply-To): /', $line ) ) {
-				if ( preg_match('|[a-z0-9_.-]+@[a-z0-9_.-]+(?!.*<)|i', $line, $matches) )
-					$author = $matches[0];
-				else
-					$author = trim($line);
-				$author = sanitize_email($author);
-				if ( is_email($author) ) {
-					echo '<p>' . sprintf(__('Author is %s'), $author) . '</p>';
-					$userdata = get_user_by('email', $author);
-					if ( ! empty( $userdata ) ) {
-						$post_author = $userdata->ID;
-						$author_found = true;
-					}
-				}
-			}
-
-			if (preg_match('/Date: /i', $line)) { // of the form '20 Mar 2002 20:32:37'
-				$ddate = trim($line);
-				$ddate = str_replace('Date: ', '', $ddate);
-				if (strpos($ddate, ',')) {
-					$ddate = trim(substr($ddate, strpos($ddate, ',') + 1, strlen($ddate)));
-				}
-				$date_arr = explode(' ', $ddate);
-				$date_time = explode(':', $date_arr[3]);
-
-				$ddate_H = $date_time[0];
-				$ddate_i = $date_time[1];
-				$ddate_s = $date_time[2];
-
-				$ddate_m = $date_arr[1];
-				$ddate_d = $date_arr[0];
-				$ddate_Y = $date_arr[2];
-				for ( $j = 0; $j < 12; $j++ ) {
-					if ( $ddate_m == $dmonths[$j] ) {
-						$ddate_m = $j+1;
-					}
-				}
-
-				$time_zn = intval($date_arr[4]) * 36;
-				$ddate_U = gmmktime($ddate_H, $ddate_i, $ddate_s, $ddate_m, $ddate_d, $ddate_Y);
-				$ddate_U = $ddate_U - $time_zn;
-				$post_date = gmdate('Y-m-d H:i:s', $ddate_U + $time_difference);
-				$post_date_gmt = gmdate('Y-m-d H:i:s', $ddate_U);
-			}
-		}
-	}
-
-	// Set $post_status based on $author_found and on author's publish_posts capability
-	if ( $author_found ) {
-		$user = new WP_User($post_author);
-		$post_status = ( $user->has_cap('publish_posts') ) ? 'publish' : 'pending';
-	} else {
-		// Author not found in DB, set status to pending. Author already set to admin.
-		$post_status = 'pending';
-	}
-
-	$subject = trim($subject);
-
-	if ( $content_type == 'multipart/alternative' ) {
-		$content = explode('--'.$boundary, $content);
-		$content = $content[2];
-
-		// Match case-insensitive content-transfer-encoding.
-		if ( preg_match( '/Content-Transfer-Encoding: quoted-printable/i', $content, $delim) ) {
-			$content = explode($delim[0], $content);
-			$content = $content[1];
-		}
-		$content = strip_tags($content, '<img><p><br><i><b><u><em><strong><strike><font><span><div>');
-	}
-	$content = trim($content);
-
-	/**
-	 * Filter the original content of the email.
-	 *
-	 * Give Post-By-Email extending plugins full access to the content, either
-	 * the raw content, or the content of the last quoted-printable section.
-	 *
-	 * @since 2.8.0
-	 *
-	 * @param string $content The original email content.
-	 */
-	$content = apply_filters( 'wp_mail_original_content', $content );
-
-	if ( false !== stripos($content_transfer_encoding, "quoted-printable") ) {
-		$content = quoted_printable_decode($content);
-	}
-
-	if ( function_exists('iconv') && ! empty( $charset ) ) {
-		$content = iconv($charset, get_option('blog_charset'), $content);
-	}
-
-	// Captures any text in the body after $phone_delim as the body
-	$content = explode($phone_delim, $content);
-	$content = empty( $content[1] ) ? $content[0] : $content[1];
-
-	$content = trim($content);
-
-	/**
-	 * Filter the content of the post submitted by email before saving.
-	 *
-	 * @since 1.2.0
-	 *
-	 * @param string $content The email content.
-	 */
-	$post_content = apply_filters( 'phone_content', $content );
-
-	$post_title = xmlrpc_getposttitle($content);
-
-	if ($post_title == '') $post_title = $subject;
-
-	$post_category = array(get_option('default_email_category'));
-
-	$post_data = compact('post_content','post_title','post_date','post_date_gmt','post_author','post_category', 'post_status');
-	$post_data = wp_slash($post_data);
-
-	$post_ID = wp_insert_post($post_data);
-	if ( is_wp_error( $post_ID ) )
-		echo "\n" . $post_ID->get_error_message();
-
-	// We couldn't post, for whatever reason. Better move forward to the next email.
-	if ( empty( $post_ID ) )
-		continue;
-
-	/**
-	 * Fires after a post submitted by email is published.
-	 *
-	 * @since 1.2.0
-	 *
-	 * @param int $post_ID The post ID.
-	 */
-	do_action( 'publish_phone', $post_ID );
-
-	echo "\n<p>" . sprintf(__('<strong>Author:</strong> %s'), esc_html($post_author)) . '</p>';
-	echo "\n<p>" . sprintf(__('<strong>Posted title:</strong> %s'), esc_html($post_title)) . '</p>';
-
-	if(!$pop3->delete($i)) {
-		echo '<p>' . sprintf(__('Oops: %s'), esc_html($pop3->ERROR)) . '</p>';
-		$pop3->reset();
-		exit;
-	} else {
-		echo '<p>' . sprintf(__('Mission complete. Message <strong>%s</strong> deleted.'), $i) . '</p>';
-	}
-
-}
-
-$pop3->quit();
