Depending on how shady the collector is...they can mail it to you at your last known address...or ANY address for that matter. If you don't acknowledge getting it, they can & will win by default. Then, you'll have to fight to get that default win reversed.

Like "they" say...You can run, but...you can't hide. They'll eventually find you. ;)

While it is *possible* that they can sneak around behind you back and get a default judgement without you knowing it, it is getting more and more highly unlikely (due to New York State Attorney General Andrew Cuomo's investigations). Process services (NOT the collector) are required to file an affidavit that they gave you the summons in the manner legally permissible in your particular jurisdiction. But you don't want a sneaky default judgement happening because you will likely only find out about it after your wages get garnished, a lien put on your home, etc. and it will take some time and a lot of headache to get it overthrown.

They will likely attempt a skip trace and will find you eventually. As long as you use your Social Security number, you are locatable. But, since you did say it is an "old debt", perhaps they won't find you until after the SOL has run out!