I've emailed quite a few people and have been very surprised at the 100% reply rate I've received and in some instances, the conversations that have developed from them.
The emails are usually very short, personalised messages along the lines of "Hi X, thank you very much for Y. It had a positive impact on me because of Z. All the best"
Some of the people include small to medium sized musicians, authors, developers, and teachers.
I kind of feel like a bit of a weirdo doing it because I don't really hear of many people who do the same. But sometimes I just genuinely want to thank a person for what they've contributed.