you get two mails as you still have enable registration notification on (you can change this in admin->site settings->user account settings. However you can't change that the user get's a notification as that is automatically done when a user is created -take a look at DNN Platform\Library\Entities\Modules\UserModuleBase.cs

if (PortalSettings.EnableRegisterNotification || PortalSettings.UserRegistration == (int)Globals.PortalRegistrationType.PrivateRegistration)

{

strMessage += Mail.SendMail(newUser, MessageType.UserRegistrationAdmin, PortalSettings);

SendAdminNotification(newUser, PortalSettings);

}

var loginStatus = UserLoginStatus.LOGIN_FAILURE;

//complete registration

switch (PortalSettings.UserRegistration)

{

case (int) Globals.PortalRegistrationType.PrivateRegistration:

strMessage += Mail.SendMail(newUser, MessageType.UserRegistrationPrivate, PortalSettings);

//show a message that a portal administrator has to verify the user credentials

if (string.IsNullOrEmpty(strMessage))

{

strMessage += string.Format(Localization.GetString("PrivateConfirmationMessage", Localization.SharedResourceFile), newUser.Email);

message = ModuleMessage.ModuleMessageType.GreenSuccess;

}

break;

case (int) Globals.PortalRegistrationType.PublicRegistration:

Mail.SendMail(newUser, MessageType.UserRegistrationPublic, PortalSettings);

UserController.UserLogin(PortalSettings.PortalId, newUser.Username, newUser.Membership.Password, "", PortalSettings.PortalName, "", ref loginStatus, false);

break;

case (int) Globals.PortalRegistrationType.VerifiedRegistration:

Mail.SendMail(newUser, MessageType.UserRegistrationVerified, PortalSettings);

UserController.UserLogin(PortalSettings.PortalId, newUser.Username, newUser.Membership.Password, "", PortalSettings.PortalName, "", ref loginStatus, false);

break;

}