Is it safe to give my email address to a service like ‘haveibeenpwned’ in light of the publication of "Collection #1"?

Troy Hunt has explained this question many times on his blog, on Twitter, and in the FAQs of haveibeenpwned.com

See here: And from the FAQ: We can certainly trust Troy on his claims, as we can not prove that he is not doing something else when handling your request. Of course, we have to trust Troy Hunt on his claims, as we have no way of proving that he is not doing something else when handling your specific request. But let's suppose we don't trust Troy: what do you have to lose? You might disclose your email address to him. How big of a risk is that to you, when you can just enter any email address you want? HIBP is a free service for you(!) that costs Troy Hunt money at the end of the day. You can choose to search through all the password databases of the world yourself if you don't want to take the risk that may be a lot of people are wrong about Troy Hunt, just because then you would disclose your email address.