There are two different words, with two different meanings; check your dictionary. Your spell-checker clearly knows only one of them, and that would be the more common one; it's spelled with an "e". If you are using the other one a great deal, you are likely a lawyer or a lawmaker or both.I am used to spelling it without the e but all the damn spell-checkers keep telling me to add the e!
Please help, why can't we all just use the same English language damn-it! Why do [not "does"] there have to be variants?
Mmm .. I wouldn't say that was "the preferred, possibly the correct, version", boozer. Faced with your sentence, I'd definitely correct the "therefore" to "therefor".I think historically "therefore" and "therefor" are the same word, if one looks at the meaning. I also agree that "therefore" is the preferred, possibly the correct, version even in cases where "therefor" is used like this:
"on receipt of the goods the buyer shall effect immediate payment therefore"
although that certainly does not follow the usual pattern: thereby, therein, thereafter, etc.