A client of ours uses Thunderbird to host their email. They have had issues in the past with people using their email to send spam. Originally they just created a new email an moved on. Now the issue is happening again, where they get hundreds of postmaster responses when they open their email. They are also unable to send out emails. We plan on changing the password for the email, but it seems like their email has been wholly marked as spam even though it isn't. Do we need to contact the ISP, is there something to be done through Thunderbird?