Error Sending Mail from Postfix: 'Must Issue a STARTTLS Command First' Due to Cisco PIX Relay Device

Issue

• Users are facing an error when attempting to send emails through the Postfix mail server, receiving the message: "530 #5.7.0 Must issue a STARTTLS command first."

• Due to the error 530 #5.7.0 Must issue a STARTTLS command first, the Postfix mail server is unable to establish secure connections, causing outgoing emails to fail and resulting in communication disruptions.

• The server returns the error 530 #5.7.0 Must issue a STARTTLS command first., this indicates that the server is unable to initiate a secure connection.

• The Postfixlogs show entries indicating that the Cisco PIX device is interfering with the SMTP communication, leading to the failure of the STARTTLS command.

  Oct 29 15:05:12 mailserver postfix/smtp[1005411]: EB05C8076XX: enabling PIX workarounds: disable_esmtp for relay.example.com[1.2.3.4]:25
  Oct 29 15:05:12 mailserver postfix/smtp[1005383]: EA8C48076XX: to=<ganeshp@example.com>, relay=relay.example.com[1.2.3.4]:25, delay=0.13, delays=0/0/0.13/0, dsn=5.0.0, status=bounced (host relay.example.com[1.2.3.4] refused to talk to me: 530 #5.7.0 Must issue a STARTTLS command first)
  Oct 29 15:05:12 mailserver postfix/qmgr[3052490]: EA8C48076XX: removed