Second about sharing website URL. I'd generally advise against giving out admin perms unless you trust whoever it is

Can you temporarily disable the extension that blocks fake/throwaway emails?

SteveXu200512 You need to be reminded that you cannot speak Chinese alone outside the theme of the Chinese language pack. . . You need to attach an English translation. . . This is Flarum's forum rules.

需要提醒您一下，在中文语言包主题外不能单独说中文。。。您需要附加英文翻译。。。这是Flarum 的论坛规则。我已经注册了您的论坛，我这就前去查看。

      So I've confirmed this, but if I may be honest, I think this is caused by an extension. Can you try disabling all extensions and trying again?

        Thanks, let me know when you do so so that I can check again

        Start enabling them 1-by-1, and testing each time. We can conclude that the issue is caused by some extension. Post which one here so that we can file an issue with the extension on github

          askvortsov After investigation, it was caused by the Close extension. Sorry I can't provide you with server logs, I'm not the administrator of the server (I don't know the password).（经过排查，是 close 扩展导致的问题。）
          URL ↓
          GitHub；