The MS Proofing Tools subkey defines spelling values for Mail. This is the Registry path for this subkey:
HKEY_CURRENT_USER\Software\Microsoft\Mail\MS Proofing Tools
CustomDict REG_SZ entry name
Specifies the name of an entry in the [MS Proofing Tools] section of the WIN.INI file. That entry in turn gives the fully qualified path to a file containing your custom dictionary. The custom dictionary contains spellings not found in the standard dictionary but that were added using the Add button in the Spelling dialog box. This entry lets Mail take advantage of a custom dictionary you may have already created with another Microsoft application, such as Microsoft Word for Windows.
Default: (no default)
Spelling REG_SZ keyname
Specifies the name of an entry in the MS Proofing Tools subkey that defines filenames for the spelling checker DLL and dictionary. The entries for Spelling are in this format:
Spelling NNNN,M
There is no space after the comma. In this format, NNNN is the four-digit language identifier of the current Windows NT version as defined in the Control\NLS\Language subkey, and M is the spelling dictionary type.
The Registry path for the key that this entry refers to is the following, by default:
HKEY_CURRENT_USER\Software\Microsoft\Mail\MS Proofing Tools
This subkey contains an entry in the following form:
Spelling NNNN,0 REG_SZ DLLfilename, Dictionary filename
Specifies the fully qualified path to the spelling checker DLL and dictionary. This entry lets Mail use the same dictionary you may already be using with another Microsoft application, such as Microsoft Word for Windows. Windows NT does supply a dictionary.
Default: MSPELL32.DLL,MSP32_XX.LEX (In these values, XX is usually the two letters identifying the language version of Windows NT defined in the DosKeybCodes subkey, as described in "Keyboard Layout Entries," earlier in this chapter.)