Apologies if I misunderstood. I am right in thinking the sequence of events is:
1. someone fills in an online form requesting a newsletter from you. But they give a false/spam trap email address.
2. You send a single "please confirm" email to that address. The pc email contains a sign-up verification code, or activation URL, or whatever.
3. You get no response to that, so you send no newsletters.
4. Your email company complains on the basis of that one pc email.
If so, you have no worries. Tell em you've used due diligence and all should be well.
A variant scenario on that is that someone did step 1 many times all with the same false email address. If you did not filter those out, then you will have sent multiple step 2 emails. That's not good. But you should get away with an apology/explanation and a tightening up of your procedures.
However, if you took the step 1 false email as an opt-in and sent multiple newsletters to the email address: that doesn't look so good. You've got some serious grovelling and procedure tightening to do.