You can only do one month at a time on the built in reports. You can choose previous month to see older data, but the reports only do a month at a time. You can use offbox reporting with something like McAfee SIEM or use ePO to run longer reports.
If we are not able to find the detail view of the email in MEG/Reports/Email Reports/detail view that what could be the reason?
Like we could see the reports from epo or SIEM, i know but if we couldn't see teh detailed report of the email in the MEG that is not 1 month older.