I'll make up stuff in between questions.
1. User choose the question to modify.
( I selected Question 25)
2. System displays the selected question details
(What is your Breath Date ?) - Oops ... spelling error
3. User makes necessary changes and submits.
(What is your Birth Date ?)
4. System validates and saves, show confirmation message.
("Your Birth Date Has Been Updated")
Now, your requirement says "Questions are been modified and email is triggered only if the email option is selected".
You could have some Options ... but make sure in the user's profile (settings) they have entered their email address.
(1) Now list options that the user wants to receive emails on and check that box.
a. Company News Letters.
b. Schedule changes.
c. Questions have been modified. X (Checked Box)
d. Your fired letter.
I selected Option "C" ... Unfortunately when questions from Any and ALL questionnaires and topics get updated, the system will run some program at the end of the day to scan all users and send the Email Notification if they have that box is checked.
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Or, maybe the user only wants an Email on certain questions or topics that have been updated (Not All).
Look at the Bottom Left of this comment page when you are writing a question or response (you won't see it otherwise), there is a "Notification Box" to check if you want an email sent to you if they answered your question in this specific forum and not everything else ... a big company could easily fill your email box up by using a General check box (first option above) and they send you an email to all updates ... whether you care or don't care about them ... you get them and have to scan and delete them from your email.
The "Notification Box" here says they will "Email you when the post has a response" ... that way you might not get any emails or you might get 100's of emails based on this question only.
I have that Box Checked ... and somewhere the system stored that in my user profile for further use.