Did you check the "Send a reminder" functionality of MantisBT?

The proper way to handle what you are asking for is to create a plugin (see also http://www.mantisbt.org/forums/viewtopic.php?f=3&t=7589 ).
You need to create a plugin that can hold one or more email addresses that get an email based upon certain changes. The developers already have made a provision for this as can be seen in core\email_api.php.
There is a signal_event which allow for exactly this:
$t_recipients_include_data = event_signal( 'EVENT_NOTIFY_USER_INCLUDE', array( $p_bug_id, $p_notify_type ) );
So the pluging would need to address the above event and with some additional coding you would be in business.

thanks all, i had been to learn that thread ans replies. i know how to solve this problem.

many thanks in advance

I don't know if it will help, but I wrote a plug-in which provides a similar functionality. My need was to send a copy of all mails to a unique mailbox
http://code.google.com/p/mantisbt-usercc-plugin/

By default, Mantis will send mails to the following

• issue reporter
• issue handler
• people who added notes
• people who are monitoring the issue

However, the mails are sent individually to each user, so you don't see other recipients on CC list (this is by design)

@jeckyll, I encourage you to host your plugin on github, in the mantisbt-plugins org instead of google code. Send a message to the mantisbt-dev mailing list if you are interested.

@degrad: thanks for your feedback I put foward this to mantisbt-dev mailing list

update: my mail was rejected. I take note of your advice and if I can figure out how to do this I will consider moving to github