You can use an SSL certificate for a domain alias in Google apps. First add and verify the domain as an alias domain of your apps account, then follow the normal procedure of adding the app and cert.
Be aware that you cannot send email from the alias domain without adding specific users as Appengine users. You could also look at mailgun or sendgrid etc. -- You received this message because you are subscribed to the Google Groups "Google App Engine" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/google-appengine. To view this discussion on the web visit https://groups.google.com/d/msgid/google-appengine/5f3cef4f-c9f2-4135-b970-05e342aa5266%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
