Hi Adhiyan,
Sorry but this is not correct actually.
You mislead the meta tag parameter put in some report/webApp objects and the under the underlying IE engine version used.
For instance, reports generate as meta tag:
<meta http-equiv="X-UA-Compatible" content="IE=9"/>
which means that the content is intended to be used/compliant for IE9 or over.
It doesn't mean the underlying engine used by Adobe Campaign rich client.
For webApp, it depends if you use the webApp v5 page (compatibility object, in 2nd tab) or the new webApp page (1st tab) as for Landing page or registration form based on this object, in the latter case, there are no meta tags generated for IE content at all.
(Of course someone can force meta tag in the webApp v6 code, but it is not useful and interpreted by browsers because it is generated after the remaining head part.)
I found the exact build for which underlying engine IE11 was first compatible: build 8622 January 2015:https://docs.campaign.adobe.com/doc/AC/en/RN_legacy.html
Adobe Campaign Release Notes
BR
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