Try to respect your candidates' time, especially those who've reached the last stage of your interviewing process. Remember, the candidate has agreed to do free work (technical task) in the hopes of demonstrating their worth. I think many candidates would agree that one of the most disrespectful things a potential employer could do would be to offer zero feedback when they turn them down. Every candidate, whether you like them or not, deserves, at the very minimum, some level of earnest feedback. Try to put yourself in the shoes of a candidate who agreed to work for free, in hopes of getting an offer. If they weren't up to the your standards, or did something wrong, then they have no way of knowing what to improve on, if you don’t give them them any feedback. Leaving a candidate in that predicament, or even being oblivious to that kind of outcome says a lot about a company. Some companies find it more respectful to follow up with a candidate over a call, as it gives them a chance to hear the candidate's perspective on the interview and process, as well as offer the candidate feedback, regardless of the outcome. I hope this helps, and I wish you nothing but success.