Did you add a reply address? If so: are you getting any exceptions on that address. If you feel that the receiving party might not be a reliable one, you definitely want the reply address to be a different server so that the mail server can reliably send you error messages.
If you've done that, checked the logs (possibly post the exceptions?) and still feel that the mailserver is malfunctioning you can file a ticket.
I managed to get the Application to send e-mails to my mail address using the SMTP settings: localhost on port 25. I now get e-mails but cant activate the account from the link back to the application.
This is the link I have in the e-mail:
It seems that it tries to activate using my local http settings to find a way back to the Cloud Application, and then fails? Is there a setting I need to change?