The most helpful thing I've used in the real world is something that looks for common typographical errors, even if the email is technically valid. Like, if th

The most helpful thing I've used in the real world is something that looks for common typographical errors, even if the email is technically valid. Like, if the user types "john.doe@gnail.com", it pops a dialogue asking "Did you mean john.doe@gmail.com?". But lets them keep what they typed, or do a different fix if needed. I found some JS called "mailcheck": https://github.com/mailcheck/mailcheck https://github.com/mailcheck/mailcheck I assume it's using popularity statistics, edit distance, etc, to come up with suggestions. There are updated clones that use react, vue, etc, instead of jquery. With a working ecommerce site, this improved the percentage of correct emails more than anything else I tried, and I had tried many things. Because it's a bad situation when you've taken someone's money and have nothing other than a shipping address to contact them if something goes wrong (bad shipping address, out of stock situation, etc).