eDiscovery for email attachment with encrypted sensitivity labels

We are currently testing encrypted sensitivity labels in conjunction with eDiscovery. We applied an encrypted label to a document, and eDiscovery was able to successfully search for the content in both OneDrive and SharePoint. However, the same functionality does not appear to work for email attachments—the content of encrypted attachments is not searchable.

Are there any specific settings or configurations that need to be enabled to support encrypted email attachments in eDiscovery?

Thanks