To comply with DMCA, we need a guaranteed way to contact publishers of content on crates.io. We've added the ability to verify your email address associated with your crates.io account, and we're going to require a verified email address to be able to cargo publish to crates.io starting on 2019-02-28 (coinciding with the release of Rust 1.33.0).

Starting with stable Rust 1.32.0 that will be released on 2019-01-17, if you run cargo publish using stable Rust and you have not verified an email address, the publish will work but you'll see a warning encouraging you to verify an email address before 2019-02-28. We'll warn for that whole release cycle. The warning will look something like this (exact wording is yet to be determined):

Starting on that date, if you run cargo publish with any Rust version and have not verified an email address, the publish won't work and you'll get an error that says you need to verify an email address. The error will look something like this (exact wording is yet to be determined):

You can verify or change your email at any time by logging in to crates.io, clicking on your icon/name in the upper right, choosing "Account Settings" from the menu, and going to the "User Email" section.

Some implementation details: