When people comment or answer, I no longer receive email notifications. Why?
You only receive email notifications if:
You have first enabled email notifications in the global inbox:
And you have not clicked on the global inbox for the specified time period. In other words, if you specified "daily" then you must not have clicked on the inbox with your mouse for at least 24 hours to begin getting email notifications. In other words, every single click on the global inbox resets this timer to zero.
You shouldn't get email notifications immediately. You should get Stack Exchange Inbox messages and (daily|each 3 hours|weekly) notifications by email if you requested them. Are you sure you have selected "Would you like to have responses to your questions sent to you via email?" when sending a question?