I would like to be able to use different mail servers to send different emails, for instance:
- all transactional emails (contribution receipt, event registration...) sent by our mail server, all mass mailing sent using mandrill
- all the emails sent by firstname.lastname@example.org are pushed through mandrill, but those sent by email@example.com via our own mail server
- do A/B testing between two different mail providers to see if mailjet or mailchimps provide better deliverability
I do think it would need some coding, either as extension or to modify civicrm core, but would love to be proven wrong.
Assuming we need to add this feature, would it be useful for you too?