This blocks any unwanted PM's from people you may not know, or may not want to speak to while allowing anyone on the accept list to PM you.

If you want to allow somebody, just type:
/addnick [NICK]

To delete somebody, it's:
/delnick [NICK]

To view the list in an @window its:
/shownicks

I had help with the shownicks alias, thanks Shawn <3

EDIT: Had a bit of a bug when being pm'd. The search wasn't working so all pm's were blocked. Fixed that now.

Alias AddNick {
  if ($1 isin $read(acceptednicks.txt, s, $1)) { 
  echo -a 7 $+ $1 is already on Accepted Nicks | halt }
  else { write AcceptedNicks.txt $1 $1
    echo -a 7 $+ $1 added to Accepted Nicks
  }
}
Alias DelNick {
  if ($1 isin $read(acceptednicks.txt, s, $1)) {
    write -ds $1 AcceptedNicks.txt 
  echo -a 7 $+ $1 deleted from Accepted Nicks | halt }
  else { echo -a 7 $+ $1 is not in Accepted Nicks
  }
}
Alias ShowNicks {
  if (!$window(@AcceptedNicks)) { window -znkg1 @AcceptedNicks }
  var %x $Lines(acceptednicks.txt)
  while (%x) { //echo @AcceptedNicks $gettok($read(acceptednicks.txt,%x),1,32) | dec %x }
}
on ^1:OPEN:?:*: {
    if ($read(AcceptedNicks.txt, s, $nick)) { msg $nick 7Please wait, i will read this sooner or later :p }
  else { msg $nick 7This is a PM Blocker. I'm sure you can guess what it does.. | /halt
  }
}