Hi Rivaldo,
If your list is opt-in and legit then check
GetRepsonse - we offer a free trial and 20k emails are certainly not a problem. However, any legit ESP is going to want to confirm that your list is an opt-in list either by sending out confirmation emails to the subscribers or testing it - with us, you can ask support to have our compliance team test the list to be sure it's healthy and then if that is proven to be the case we will waive the confirmation process.
A legit opt-in list is pure gold and well worth the effort to build it.
Regards,
jim