> ok begin
> quiet change * [log in to unmask] [log in to unmask]
> quiet change * [log in to unmask] [log in to unmask]
> ... etc. ...
> ok end

This is probably the best way to go about it. You may want to break it down in smaller jobs, presumably around 1,000 addresses, and avoid running them during peak hours :-) If you have thousands of lists or older hardware, it may be best to make a test with 100 addresses and see how fast that goes. For reference, with 20k lists and HPO:

time quiet change * [log in to unmask] [log in to unmask]
* There is no subscription for [log in to unmask] in any of the lists you
* specified.
VCPU=0.010 TCPU=0.020 T-V=0.010 Elapsed: 0.019 sec

sh hw
* CPU model: 4-CPU 3.16GHz Xeon X5460 (2G)

  Eric