Unable to send emails html box is missing after 3.5 upgrade

Remove HTML editor from control panel and re-install HTML Proclaim component manually.
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To remove the HTML Editor follow the steps below:
1. Go into Control Panel
2. Navigate to Programs and features
3. Find the HTML Editor and uninstall it
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And then to Reinstall the HTML Editor:
1. Log in to PC as Administrator
2. Reduce the User Account Control Setting to Never Notify
3. Navigate to the proclaim install folder, you can do this manually by going in servername:\\prodisk\proclaim\foldername install\cd\proclaim components\htmleditor and find the HTMLEditor-Proclaim .exe and run as admin
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​Warning: Your IT may need to carry out the reinstall of the HTML editor if you do not have the correct permissions.
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If your issue is still happening after doing the above, please raise a new case online and reference the title of this article.