Looks like there’s an open mail relay hosted in the DPRK. Masked the domain for privacy reasons. Only resolves to DPRK domains.

Resolving hostname…
Connecting…
Connection: opening to smtp.XXXXXX.kp:25, timeout=300, options=array (
)
Connection: opened
SERVER -> CLIENT: 220 mail.star-co.net.kp ESMTP Postfix
CLIENT -> SERVER: EHLO tools.wormly.com
SERVER -> CLIENT: 250-mail.star-co.net.kp
250-PIPELINING
250-SIZE 1000000000
250-VRFY
250-ETRN
250-ENHANCEDSTATUSCODES
250-8BITMIME
250-DSN
250 SMTPUTF8
CLIENT -> SERVER: MAIL FROM:
SERVER -> CLIENT: 250 2.1.0 Ok
CLIENT -> SERVER: RCPT TO:
SERVER -> CLIENT: 250 2.1.5 Ok
CLIENT -> SERVER: DATA
SERVER -> CLIENT: 354 End data with .
CLIENT -> SERVER: Date: Mon, 29 Apr 2019 02:58:14 +0000
CLIENT -> SERVER: To: flph@star-co.net.kp
CLIENT -> SERVER: From: Wormly SMTP Test
CLIENT -> SERVER: Subject: Wormly SMTP Test Message
CLIENT -> SERVER: Message-ID: <513d1d6870dbfc59c46586d3494dcc8c@blog.wormly.com>
CLIENT -> SERVER: MIME-Version: 1.0
CLIENT -> SERVER: Content-Type: text/plain; charset=iso-8859-1
CLIENT -> SERVER:
CLIENT -> SERVER: This message was sent using the Wormly SMTP testing tool by this user:
CLIENT -> SERVER: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:63.0) Gecko/20100101 Firefox/63.0
CLIENT -> SERVER: 185.210.218.100
CLIENT -> SERVER:
CLIENT -> SERVER: .
SERVER -> CLIENT: 250 2.0.0 Ok: queued as 5AF6222C37A4
CLIENT -> SERVER: QUIT
SERVER -> CLIENT: 221 2.0.0 Bye
Connection: closed
Message completed successfully.