using two outgoing email servers

I’m trying to using two different outgoing email servers. One for sending email campaigns ( i.e via mandrill) and the other to send customer support email. I have setted the system outgoing email to mandrill, so all system related emails (included campaigns) can use mandrill and i unchecked the option “Allow users to use this account for outgoing email”. So each users can customize his account.
Then i have configured the system email setting per user. But it uses always mandrill and i can change only email and password (not server).
I have also tried to add another outgoing server to user via Email->setting->email Account but it seems don’t be used.
Is there a way to accomplish what i’m looking for?