[MlMt] can MessageVerifications.plist catch "is not among"?

[Shoshanna Green]

Is there a way to set up a test in MessageVerifications.plist that will 
fire when an element is not included in a specified list or set? What I 
want is to set up a test like

{
    title = "Message is going to an unapproved recipient.";
    details = "Verify that you want to send it!";
    conditions = "(from ~[c] 'my_private_address at example.com' and
                              #recipient.address IS NOT AMONG
                                                       friend_1 at example.com,
                                                       friend_2 at example.com,
                                                       friend_3 at example.com,
                                                       friend_4 at example.com)"
}

Currently I have this kludged by putting the list of good addresses in 
the TO line of a dummy draft message in a dummy account and writing a 
condition as follows

{
    title = "Message is going to an unapproved recipient.";
    details = "Verify that you want to send it!";
    conditions = "(from ~[c] 'my_private_address at example.com' and
                              #recipient.address !=[c] 
$'imap://dummy_account@imap.example.com/list_of_friends_addresses'.#recipient.address)"
}

but this is awkward to read and maintain, especially since the actual 
list of approved recipients is more than 130 addresses long. I'd much 
rather have it in MessageVerifications.plist than in the header of a 
dummy email message, if possible!

Shoshanna Green
shoshannag at gmail.com