External customers and outgoing (SMTP) mail configuration in cloud

As a support team member I am looking for a solution to serve our internal and especially our external customers.

I have set up your cloud solution Service Desk. I have read documentation, faqs, googled etc. but my three days experience does not pull out an answer to my questions.

I want external customers to have possibility to send and receive email to/from system. So far I haven't figured out how to get emails going to (again external)customers from our pre-defined email address sent by Jira SD system. Incoming mail works as expected. There's no option to configure outgoing mail server. Why?

I do not care what is the way to solve this inside your cloud but it is a show stopper for us if it is not possible.

Best Regards,

Kimmo Häyrinen