When the job ends triggering the email,

it is occasionally sent successfully, and occasionally the transmission fails.

I found that the mailbox server authentication needs to be re-authenticated after 30s,

and the email-ext-plugin timeout is 60s;
In the system management,

the first time the email was sent successfully,
The second time the mail is sent is between the mailbox server authentication requires re-authentication and the email-ext-plugin has not timed out, and the mail fails to be sent.