Using lmtp to authenticate email users

[Patrick Mahan]

FreeBSD 11.2
Postfix 3.3.2
Dovecot 2.3.4

I am trying to use dovecot lmtp with postfix to verify authentication of
incoming email and to avoid being a spam relay (an issue I was having using
sendmail as my MTA).

I am getting the following log message in /var/log/maillog:

Mar 30 20:31:38 ns postfix/smtpd[40373]: NOQUEUE: reject: RCPT from
mail-eopbgr750091.outbound.protection.outlook.com[40.107.75.91]: 450 4.1.1 <
mahan at mahan.org>: Recipient address rejected: unverified address: host
ns.mahan.org[private/dovecot-lmtp] said: 550 5.1.1 <mahan at mahan.org> User
doesn't exist: mahan at mahan.org (in reply to RCPT TO command); from=<
pmahan at silver-peak.com> to=<mahan at mahan.org> proto=ESMTP helo=<
NAM02-BL2-obe.outbound.protection.outlook.com>

'mahan' does exist on ns.mahan.org.  So I am confused to why lmtp is
failing to find this username.

Thanks,

Patrick
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