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Clients are, "Unable to use the Ignore or Add To Dictionary options in Spelling & Grammar window" when sending an email message.
This symptom will normally present itself after updating Windows 10 to version 1703.
Microsoft is aware of the issue and is working on a permanent solution (May, 2017):
https://support.office.com/en-us/article/Unable-to-use-the-Ignore-or-Add-To-Dictionary-options-in-Spelling-Grammar-window-f594a013-28ee-44dc-af16-32853d51443a?ui=en-US&rs=en-US&ad=US
In the meantime, click the Undo Edit button to enable the Ignore All and Add To buttons.
