@[deleted]If you disable the outbound SMTP settings in OSticket, it will default to use the PHP mail() function, which you can then point at whatever you want. On a linux server that usually means it hits the local mail service, such as postfix, and there's a very good tutorial here on setting up postfix to send via mandrilapp:https://mandrill.zendesk.com/hc/en-us/articles/205582187-Can-I-configure-Postfix-to-send-through-Mandrill-If you do use mandrillapp I would suggest you jump through the hoops of getting DKIM authentication on your domains, as Mandrill will clearly say in the email headers that they aren't you and are just sending for you which results in a "Sent on behalf of... " message in the FROM: field in most email clients (like gmail). Once you set up DKIM for your domain, this goes away.