Updating website forms

Our Internet service provider recently made changes which have disabled our website forms - "our recent decision to enforce the policy we had in place for sending emails from websites. We undertook the decision to immediately enforce the criteria due to the increasing amount of spam that has been sent via emails from websites as this led to our Mail IP's being regularly blocked which in turn had an impact on our Mail services." The Service Provider has not been helpful in advising us how to fix our forms other than to give updated SMTP and Port information for the Forms, which we still cannot get to work. So we need some help quickly. The project is to get all the forms working again as soon as possible - we are losing business (either using the same open source code as used before, or to replace them with simpler forms to do the same job) The website is [login to view URL] - please check all the forms on this site "Open a New Account" etc and you will see a 503 or internal service error. Successful applicants will have the chance to modernise/update all our other websites, We are currently not using databases on our sites.