Pay-per-subscriber services are companies that go out and
get opt-in subscribers to your newsletter. You pay them
a small fee per subscriber (typically $0.10 to $1.00 each,
depending on the company).
I tried one of these services myself for a few months --
and probably wouldn't do it again. The quality of the
addresses I received wasn't very high... sure, I got
some good, responsive subscribers but most of my
unsubscribe requests or bounced emails (from full
mailboxes, invalid addresses, etc) primarily came
from these purchased addresses.
Focus instead on the quality of your list, rather than
the size. I'd rather have 100 subscribers who read the
newsletter than 10,000 who either delete it or ignore it!
