Index: wp-admin/includes/schema.php
===================================================================
--- wp-admin/includes/schema.php	(revision 23185)
+++ wp-admin/includes/schema.php	(working copy)
@@ -369,10 +369,6 @@
 	'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',
@@ -476,6 +472,9 @@
 
 	// 3.5
 	'link_manager_enabled' => 0,
+
+	// 3.6
+	'post_by_email_enabled' => 0,
 	);
 
 	// 3.3
Index: wp-admin/includes/upgrade.php
===================================================================
--- wp-admin/includes/upgrade.php	(revision 23185)
+++ wp-admin/includes/upgrade.php	(working copy)
@@ -402,10 +402,15 @@
 	if ( $wp_current_db_version < 22422 )
 		upgrade_350();
 
+	if ( $wp_current_db_version < 22441 )
+		upgrade_360();
+
 	maybe_disable_link_manager();
 
 	maybe_disable_automattic_widgets();
 
+	maybe_disable_post_by_email();
+
 	update_option( 'db_version', $wp_db_version );
 	update_option( 'db_upgraded', true );
 }
@@ -1209,6 +1214,18 @@
 }
 
 /**
+ * Execute changes made in WordPress 3.6.
+ *
+ * @since 3.6.0
+ */
+function upgrade_360() {
+	global $wp_current_db_version;
+
+	if ( $wp_current_db_version < 22441 && 'mail.example.com' != get_option( 'mailserver_url' ) )
+		update_option( 'post_by_email_enabled', 1 ); // Previosuly set to 0 by populate_options()
+}
+
+/**
  * Execute network level changes
  *
  * @since 3.0.0
@@ -1953,6 +1970,18 @@
 }
 
 /**
+ * Disables Post by Email options if, at the time of upgrade, the settings have not been changed from original defaults.
+ *
+ * @since 3.6.0
+ */
+function maybe_disable_post_by_email() {
+	global $wp_current_db_version;
+
+	if ( $wp_current_db_version >= 22441 && get_option( 'post_by_email_enabled' ) && '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: wp-admin/options-writing.php
===================================================================
--- wp-admin/options-writing.php	(revision 23185)
+++ wp-admin/options-writing.php	(working copy)
@@ -28,7 +28,7 @@
 	'content' => '<p>' . __('Press This is a bookmarklet that makes it easy to blog about something you come across on the web. You can use it to just grab a link, or to post an excerpt. Press This will even allow you to choose from images included on the page and use them in your post. Just drag the Press This link on this screen to your bookmarks bar in your browser, and you&#8217;ll be on your way to easier content creation. Clicking on it while on another website opens a popup window with all these options.') . '</p>',
 ) );
 
-if ( apply_filters( 'enable_post_by_email_configuration', true ) ) {
+if ( get_option( 'post_by_email_enabled' ) && apply_filters( 'enable_post_by_email_configuration', true ) ) {
 	get_current_screen()->add_help_tab( array(
 		'id'      => 'options-postemail',
 		'title'   => __( 'Post Via Email' ),
@@ -124,7 +124,7 @@
 	<p><textarea rows="5" cols="120" readonly="readonly"><?php echo htmlspecialchars( get_shortcut_link() ); ?></textarea></p>
 </div>
 
-<?php if ( apply_filters( 'enable_post_by_email_configuration', true ) ) { ?>
+<?php if ( get_option( 'post_by_email_enabled' ) && apply_filters( 'enable_post_by_email_configuration', true ) ) { ?>
 <h3><?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>
 
Index: wp-includes/default-filters.php
===================================================================
--- wp-includes/default-filters.php	(revision 23185)
+++ wp-includes/default-filters.php	(working copy)
@@ -288,4 +288,7 @@
 // This option no longer exists; tell plugins we always support auto-embedding.
 add_filter( 'default_option_embed_autourls', '__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' );
+
 unset($filter, $action);