The imported certificate in targets | SMTP | Properties | SMTP Archiving | Change Security shows the details ('Issue to:', 'Start date:' and 'Expiry date:') of the certification authority

Instead, the SSL certificate without the 'chain hierarchy' would properly show its own details.

Note* If Microsoft Certificate Authority (CA) is being used, then export wizard can be used to export the pfx file and un-check the box for “Include all certificates in the certification path if possible” to get the pfx file imported without the Certificate chain hierarchy.
This is a known issue with pfx certificates files containing related certificates like the Certification Authority (CA).
This issue has been fixed from Enterprise Vault 12.5.3
https://www.veritas.com/content/support/en_US/downloads/update.UPD790480