/usr/share/pki/ca/emails/rnJob1Item.txt is in pki-ca 10.6.0-1ubuntu2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 | Serial number = 0x$HexSerialNumber
SubjectDN = $SubjectDN
Validity period = $NotBefore - $NotAfter
Suggested Renewal http host name = $HttpHost
Suggested Renewal http port number = $HttpPort
Renewal notification status = $Status
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