I have looked up into this.

gmail.com.br does not contain any mx server. As gmail moved all its country based email to google.com account and primary domain as gmail.com which contain the MX server points.
we made some correction here though as gmail.com.br domain still exists and warning was domain not found, so now it will say mx record not found instead. Because domain was actually exists with redirection. It was mx record who does not exists for this country specific ltd. We also added an update with MX redirection option. So you can manually assign a domain for redirection its mx server to proper one incase a provider change it or move their mx to somewhere else by completing changing or disabling a domain. This update will be visible in the next release.

Email which you provided for gmail.com.br seems does not exist and comes as invalid with undeliverable status with our development update.

Regarding your claim with yahoo.com.br, I did not notice the problem with it. Can you post the email address that has a problem at the support ticket or here?

All right buddy, thanks, yahoo.com.br has worked fine, I tried to check a list only of yahoo.com.br but it seems that they blocked my IP, nothing with script.