I think in recent years the only method they accept has been via NFPA website. You must register to use the site. NFPA will bombard you with emails and snail mail once you are on their list, whether it is things you have an interest in or not. You do have access to all free stuff they offer on the site as well though, such as ability to access current and past editions of the NEC, as well as look at current or past submittals, ROP's/ ROC's and such that may help determine why a particular code section was written the way it was at that time.