I read this on the forum here:

"As per your request, we have unblocked the user account and the user should be able to send emails without any issues. Further, please communicate only with valid and engaged accounts to avoid being blocked in the future. "

If someone is sending emails to a large list of people, there are bound to be a bunch of bounces from people who changed email providers. If that is something that blocks someone's email, that gives me a bad feeling... Are paid accounts subject to such strange "limits" which put blocks on your account that you have to become aware of and then take time to complain on the forum or something? I am a new customer and I am trying to understand the ecosystem here and blocks on things concern me when I read of them.