虽说能够绕过邮件来设定密码，但是总觉得要实现邮件功能，而且不甘心为啥别人就能设置成功呢？！俺也要弄成功，于是到官网去找帖子，功夫不负有心人，总算找到了，官网帖子推荐用GMail邮箱，二话不说，弄了个新的GMail邮箱，照着配置，果然就行啦，下面就把链接贴出来(虽说是英文，但是看懂挺容易的)http://www.mantisbt.org/forums/viewtopic.php?f=3&t=15398
稍微说一下，只需在config_inc.php文件中加入下面内容即可，
$g_allow_signup = ON; //allows the users to sign up for a new account
$g_enable_email_notification = ON; //enables the email messages
$g_phpMailer_method = PHPMAILER_METHOD_SMTP;
$g_smtp_host = 'smtp.gmail.com';
$g_smtp_connection_mode = 'tls';
$g_smtp_port = 587;
$g_smtp_username = 'youraccount@gmail.com'; //replace it with your gmail address
$g_smtp_password = '*********'; //replace it with your gmail password
$g_administrator_email = 'youradmin@whatever.com'; //this will be your administrator email address
