There are two aspects to spell checking, checking when the message is sent and checking as you type. Please refer to the section(s) that apply to your configuration.
Disabling spell checking when the message is sent | |
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You disable the spell check by de-selecting the "Spell check on sending mail" check box on the "Sending Mail" tab of the Options window (Shift+F7 or Tools->Options). |
Disabling spell check as you type | |
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You disable the spell check as you type by de-selecting the "Correct spelling errors as you type" check box on the "Spelling Options" window (Tools | Configure spelling). |
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To disable the spell as you type feature use the "Underline misspelled words as you type" option on the "Sending Mail" tab of the Options window (Shift+F7 or Tools->Options).
You can also disable spell-as-you-type: in the compose message window, go to View menu, and uncheck "Enable Spell-As-You-Type". |