code: func isRecipientAllowed(c context.Context, recipient string, build *buildbucketpb.Build) bool {
  	// TODO(mknyszek): Do a real ACL check here.
  	if strings.HasSuffix(recipient, "@google.com") || strings.HasSuffix(recipient, "@chromium.org") {
  		return true
  	}
  	logging.Warningf(c, "Address %q is not allowed to be notified of build %d", recipient, build.Id)
  	return false
  }
docs: // isRecipientAllowed returns true if the given recipient is allowed to be notified about the given build.