I'm not a native English speaker, so my interpretation may be little difficult to understand....?
I don't know whether my database smtp settings are right?
.. removed image .. modded by @luceos
I asked my friends who R useing flarum.They guess maybe I have trouble with smtp settings so I send this screenshot to them,but they don't know maybe where have wrongs.
And I searched flarum community about error 422,it seems because of too short password or incorrect username.......So I tried to use a password with upper case, lower case, numbers and over 8 characters.But seems it doesnt work at all....I also received 422 error......

So I guess there must be something wrong with my smtp settings..........
For some special reasons(Im in China) so that I cant use gmail for test...
You know, if a community cant join newer to activity it....that must be the worst thing [Q_Q]