Moonclaw wrote:- When I send myself a private message
There is no inbuilt setting for that and I'm not aware of any MOD that would do that either because it is considered that if you send yourself a message you would already know about it so there would be no need for a notification.
If you want to be automatically subscribed to topics in which you have posted there is a setting for that
User Control Panel > Board preferences > Edit posting defaults > Notify me upon replies by default
Set that to Yes
phpBB, by default, doesn't send notifications for new posts because many people may consider that to be spam. Therefore, there are options for individual members to choose.