[amp2000]

Heres what i done to my my email template so far if it helps you

Hello $touser[username],

$bbuserinfo[username] has just replied to a thread you have subscribed to entitled -
 $threadinfo[title] - in the $foruminfo[title] forum of $bbtitle.
New at $bbtitle!
You can now reply to the thread by replying to this message. All you need to do is to 
make sure this code appears in the email subject:
[thread-$threadinfo[threadid]-$touser[field5]]
You should also remove this text to ensure your reply is readable by other forum users.

This thread is located at:
$bburl/showthread.php?threadid=$threadinfo[threadid]&goto=newpost

There may be other replies also, but you will not receive any more notifications until 
you visit the board again.

Yours,
$bbtitle team

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Unsubscription information:

To unsubscribe from this thread, please visit this page:
$bburl/member2.php?action=usub&threadid=$threadinfo[threadid]

To unsubscribe from ALL threads, please visit this page:
$bburl/member2.php?action=usub&type=allthread

I'm not sure but [thread-$threadinfo[threadid]-$touser[field5]] dosent look like correct syntax to me so you might want to start there (I could be wrong though)

Let me know how you get on