Our email hosting service has a new self-policing feature that will block and suspend email accounts that attempt to send transactional or email marketing services. This includes:
- sending invoices in bulk
- sending emails individually in short periods of time that have the same subject line
- emails that contain marketing messages
These measures help protect the overall integrity of the email hosting and associated IP addresses. More, it helps ensure the sending IP addresses do not get blacklisted.
If you need a solution for sending transactional emails such as invoices, find some sources and references here:
https://www.google.com/search?q=transactional+email+smtp+service
If you need a solution for email marketing, find some sources and references here:
https://www.google.com/search?q=email+marketing+service