If you have a lot of categories you can use the copy to all categories option in the category privileges page.
78e95deb-a343-4013-9564-f63f1b5ad699-image.png
I selected all unverified users in the Users section and clicked on send validation email.
on the log, I'm getting like this
2020-12-30T11:20:34.940Z [4567/20005] - [31merror[39m: Error: Can't send mail - all recipients were rejected: 501 Invalid RCPT TO address provided
at SMTPConnection._formatError (/root/nodebb/node_modules/nodemailer/lib/smtp-connection/index.js:784:19)
at SMTPConnection._actionRCPT (/root/nodebb/node_modules/nodemailer/lib/smtp-connection/index.js:1613:28)
at SMTPConnection.<anonymous> (/root/nodebb/node_modules/nodemailer/lib/smtp-connection/index.js:1574:26)
at SMTPConnection._processResponse (/root/nodebb/node_modules/nodemailer/lib/smtp-connection/index.js:942:20)
at SMTPConnection._onData (/root/nodebb/node_modules/nodemailer/lib/smtp-connection/index.js:749:14)
at TLSSocket.SMTPConnection._onSocketData (/root/nodebb/node_modules/nodemailer/lib/smtp-connection/index.js:195:44)
at TLSSocket.emit (events.js:315:20)
at addChunk (_stream_readable.js:295:12)
at readableAddChunk (_stream_readable.js:271:9)
at TLSSocket.Readable.push (_stream_readable.js:212:10)
@varun-ganesh-d that means that for at least one the unverified users, they provided an email that doesn't exist.