I am looking for the best practices and advice on setting up Exchange 2007 (EBS environment, Edge Transport Role is on a MS Forefront/TMG server, the rest of the Exchange roles are on a dedicated server) to allow emails (newsletters and such) sent on the company's behalf from emarketing software running on a hosted server.
The Edge Transport Role server has a receive connector configured for the hosted server. SPF for the sending domain includes the hosted server's IP address.
Currently, emails go through Ok but it takes extremely long time to send them all. The number of recipients can be within a 50-80 K range.