From today I can no longer send. What should I do?

Surely if until a few moments ago Mailing List Studio sent correctly it means that it is not a problem related to the program. It's not even a licensing issue, because Mailing List Studio licenses don't expire. It's probably a problem with SMTP servers, because free SMTP servers often limit daily mailings. Send us a support file and we will verify the problem.

Mailing List Studio