By default the forum subscribes you to any thread you post in, meaning you will be emailed anytime someone replies.
If you want to turn that off, here is how.

Option 1:

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At the top right of the page on any thread you are subscribed to is a yellow button that say you are subscribed. Click it.

Option 2:

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Click your username top right, the dropdown shows settings. Click user settings.


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Click the notifications tab in user settings, and change email notifications to "Off, through my Message Center only". Click the button bottom right to save changes.