Index: devel.mail.inc
===================================================================
RCS file: devel.mail.inc
diff -N devel.mail.inc
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ devel.mail.inc	6 Nov 2009 06:50:16 -0000
@@ -0,0 +1,74 @@
+<?php
+// @Id;
+
+/**
+ * @file
+ * MailSystemInterface for logging mails to the filesystem
+ */
+
+class DevelMailLog extends DefaultMailSystem {
+
+  public function composeMessage($message) {
+    $mimeheaders = array();
+    $message['headers']['To'] = $message['to'];
+    foreach ($message['headers'] as $name => $value) {
+      $mimeheaders[] = $name . ': ' . mime_header_encode($value);
+    }
+
+    $line_endings = variable_get('mail_line_endings', MAIL_LINE_ENDINGS);
+    $output = join($line_endings, $mimeheaders) . $line_endings;
+    $output .= $message['subject'] . $line_endings;
+    $output .= preg_replace('@\r?\n@', $line_endings, $message['body']);
+    return $output;
+  }
+
+  public function getFileName($message) {
+    $output_directory = $this->getOutputDirectory();
+    $this->makeOutputDirectory($output_directory);
+
+    $output_file_format = variable_get('devel_debug_mail_file_format', '%to-%subject-%datetime.mail.txt');
+    $tokens = array(
+      '%to' => $message['to'],
+      '%subject' => $message['subject'],
+      '%datetime' => date('y-m-d_his'),
+    );
+    return $output_directory . '/' . $this->dirify(str_replace(array_keys($tokens), array_values($tokens), $output_file_format));
+  }
+
+  private function dirify($string) {
+    return preg_replace('/[^a-zA-Z0-9_\-\.@]/', '_', $string);
+  }
+  /**
+   * Save an e-mail message to a file, using Drupal variables and default settings.
+   *
+   * @see http://php.net/manual/en/function.mail.php
+   * @see drupal_mail()
+   *
+   * @param $message
+   *   A message array, as described in hook_mail_alter().
+   * @return
+   *   TRUE if the mail was successfully accepted, otherwise FALSE.
+   */
+  public function mail(array $message) {
+    $output = $this->composeMessage($message);
+    $output_file = $this->getFileName($message);
+    
+    file_put_contents($output_file, $output);
+    return $output;
+  }
+  
+  protected function makeOutputDirectory($output_directory) {
+    if (!is_dir($output_directory)) {
+      mkdir ($output_directory);
+    }
+    if (!is_writable($output_directory)) {
+      // No need to t() this up IMO.
+      throw new Exception("Unable to continue sending mail, $output_directory is not writable");
+    }
+  }
+
+  public function getOutputDirectory() {
+    return variable_get('devel_debug_mail_directory', file_directory_path() . '/mails');
+  }
+}
+?>
Index: devel.info
===================================================================
RCS file: /cvs/drupal-contrib/contributions/modules/devel/devel.info,v
retrieving revision 1.9
diff -u -p -r1.9 devel.info
--- devel.info	17 Jul 2009 11:54:59 -0000	1.9
+++ devel.info	6 Nov 2009 06:50:16 -0000
@@ -6,3 +6,5 @@ dependencies[] = menu
 core = 7.x
 files[] = devel.module
 files[] = devel.install
+files[] = devel.test
+files[] = devel.mail.inc
Index: devel.test
===================================================================
RCS file: devel.test
diff -N devel.test
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ devel.test	6 Nov 2009 06:50:16 -0000
@@ -0,0 +1,51 @@
+<?php
+// @Id;
+/**
+ * @file
+ * Tests for devel module.
+ */
+
+/**
+ * Test devel mail functionality.
+ */
+class DevelMailTest extends DrupalWebTestCase {
+
+  public static function getInfo() {
+    return array(
+      'name' => 'Devel Mail interface',
+      'description' => 'Test sending mails with debug interface',
+      'group' => 'Devel',
+    );
+  }
+
+  function setUp() {
+    parent::setUp();
+  }
+
+  /**
+   * Test mail logging functionality.
+   */
+  function testMail() {
+    require_once ('devel.mail.inc');
+    $message = array();
+    $message['to'] = 'drupal@example.com';
+    $message['subject'] = 'Test mail';
+    $message['headers'] = array(
+      'From' => 'postmaster@example.com',
+      'X-stupid' => 'dumb',
+    );
+    $message['body'] = "I am the body of this message";
+    $d = new DevelMailLog();
+
+    $filename = $d->getFileName($message);
+    $content = $d->composeMessage($message);
+    $expected_filename = $d->getOutputDirectory() . '/drupal@example.com-Test_mail-' . date('y-m-d_his') . '.mail.txt';
+    $this->assertEqual($filename, $expected_filename);
+    $this->assertEqual($content, 'From: postmaster@example.com
+X-stupid: dumb
+To: drupal@example.com
+Test mail
+I am the body of this message');
+  }
+
+}