Mine

on *:TEXT:!dns*:#:{
  if ($chan != #sa-mp) {
    if ( $2 < 127.* ) ||  ( $2 == localhost ) || (  127.0.0. isin $2 ) || ( 192.168. isin $2 ) || ( 255 isin $2 ) || ( $2 == 1.2.3.4 ) || ( $2 < 255) {
      msg $chan Unable to resolve. ( Forbidden )
      goto end
    } 
    if ( $2 isletter ) { 
      msg $chan Invalid IP address.(1)
      goto end
    }
    if ( $2 !isletter ) {
      dns $2
      set %dnschan $chan
    msg %dnschan 3Resolving: $2 }
    else {
      msg $chan Invalid IP address.(2)
      goto end
      :end
    }
  }
}
on 1:DNS:{ 
  set %rlsdns $dns(0).addr $2
  if (%rlsdns != $null) { /msg %dnschan 3Resolved: $dns(0).addr $2 }
  if (%rlsdns == $null) || (unable isin %rlsdns) {
    msg %dnschan 3Resolved: Unable to resolve.
  }
}