2016-10-07 update: we created a new knowledge base entry to replace this forum discussion.
Check it out here:
tldr; get an account on a free email delivery service (such as Mandrill); configure the SMTP credentials on Service Center: https://<YOURPERSONAL>.outsystemscloud.com/ServiceCenter/Email_Configuration.aspx
The personal environment does not include a pre-configured SMTP server so it's up to each personal environment owner to configure the SMTP serve they want to use.
One option would be to use their gmail account to send emails but WE ADVISE AGAINST IT (see this discussion for the why).
At this point we recommend that you create an account on a free email delivery service and then use the SMTP credentials provided by that service to configure your personal environment. To do this visit the page below on your personal environment and fill in the missing fields and then click Apply.
The emails won't go out immediately but you can check their status on the page below:
If the emails are stuck there for too long (and the SMTP settings are indeed correct) drop us a note at firstname.lastname@example.org so that we can help you troubleshoot the underlying issue.