Or more precisely: it only exists to make sure e-mail addresses are only used once per user (unless your board settings are "addresses can be re-used") and enforces comparing addresses only in lowercase.
"The problem is probably not my English but you do not want to understand correctly. ... We will not come anybody anyway, nevertheless, it's best to shit this." Affin, 2018-11-20 ↑
"But this shit is not here for you. You can follow with your. Maybe the question, instead, was for you, who know, so you shoved us how you are." axe70, 2020-10-10 ↑
"My reaction is not to everyone, especially to you." Raptiye, 2021-02-28 ↑