You are welcome to answer questions posted in the Ask a Teacher forum as long as your suggestions, help, and advice reflect a good understanding of the English language. If you are not a teacher, you will need to state that clearly at the top of your post. Please note, all posts are moderated by our in-house language experts, so make sure your suggestions, help, and advice house the kind of information an international language teacher would offer. If not, and your posts do not contribute to the topic in a positive way, they will be subject to deletion.
MS Word often does not know many things about human language, Peter. The sentence sounds correct to me, but if underlining is irritating for you, you can re-arrange it like that:
Thus, kindly contact AOL should you have any questions.
OR:
Thus kindly contact AOL for any queries about this.
The latter is used quite often in formal business letter or ads.
It probably thinks it's a fragment because it isn't recognising 'contact' as a verb because there's no subject, compounded by the fact that it can also be a noun. The grammar check can often recognise things wrongly as fragments.
MS Word Shows An Error 
Linear Mode
