we actually use the mail service for several forms. We have now a new requirement, where we need to use a different target for one specific reporting form.
* AFAIK not possible with OOB to configure 2 mail servers & need to implement at project level. You might need to create a custom email service. Example http://helpx.adobe.com/adobe-cq/using/creating-custom-cq-email-services.html
* One of the option to make external calls is to utilize WorkflowExternalProcess http://dev.day.com/docs/en/cq/current/javadoc/com/day/cq/workflow/exec/WorkflowExternalPro cess.html