One of my users has complained that despite all settings being reasonable
(ToolsOptionsSpelling looks OK; and Word not ticked as default mail editor
in ToolsOptionsMail Format ) spelling errors are never detected when he
hits F7 to do a spell check when replying to an email received in HTML. Can I
fix this?

Suzanne answered a question last year suggesting that the spellchecker is
switched off when one pastes something from the web--could this be related?