When sending emails, Transport Layer Security (TLS) encryption is not used because InterScan Messaging Security Virtual Appliance (IMSVA) uses HELO instead of EHLO.
You may have configured postfix to use the 'disable_esmtp' PIX workaround. Refer to smtp - Postfix SMTP+LMTP client for more details about the smtp_pix_workarounds setting.
Find out why the 'disable_esmtp' PIX workaround was previously used on IMSVA. If it is because an old PIX firmware was used, please make sure that the bug is no longer existing on the current firewall.
Reconfigure postfix to not use the 'disable_esmtp' PIX workaround:
- Edit /opt/trend/imss/postfix/etc/postfix/main.cf.
- At the bottom, add the parameter "smtp_pix_workarounds=delay_dotcrlf" (without quotation marks).
- Restart postfix:
# postfix restart "