Can the Office 365 E3 Plan be upgraded to Office 365 E4 as part of the Enterprise Cloud Suite?

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Yes, this is possible. By default, Enterprise Cloud Suite includes the Office 365 E3 Plan. In addition to it , the Office 365 E4 Plan can be obtained as an Add-on User Subscription License.

Source: Flyer_Microsoft_Enterprise Cloud Suite 2016-08-24 (German only)

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