If you got the message I sent yesterday in your email, it is because you have the option turned on indicating you wish to be advised via email of new private messages. I sent you a forum private message, not an email.
You can modify the settings for pm notifications here: https://www.susans.org/forums/index.php?action=profile;area=pmprefs
You can change the settings for topic notifications here: https://www.susans.org/forums/index.php?action=profile;area=notification
Again the control of the option to have (or not) notifications of new private messages and topic replies sent to you via email is entirely under your control. It is very rare I contact anyone via email without you, emailing me first.
You are free to disable email notifications, or request deletion; otherwise you will receive private messages like all of the other users do from time to time. This is not optional, and you cannot opt out of them.
The notification settings are nowhere to be found, when I click on the link above, I just get to see my profile page :(
You may have needed 10 posts the two options on the
https://www.susans.org/forums/index.php?action=profile;area=pmprefs page are
Receive personal messages from:
Notify by email every time you receive a personal message: