deliver an email to a large number of local users directly via doveadm

Hello,We have a mail service that uses postfix and dovecot. We would like to send an email to a large number of users(about 100K). However, it takes too long to send the email through smtp. Is there any solution to deliver the email locally to all user mailboxes directly.dovecot uses lmtp for transfering local emails. the worst solutoin is that copy the email to all mailboxes via linux file system. But we would prefer to use some tools provided by dovecot like doveadm. is there any way to do this job?