Beginning with certain date ESXi releases E1000 adapter is not supported anymore with the following Windows releases:
- Win8.x (8.0 and above)
- Windows 2012
- Windows 2012 R2 and above.
The end of support is mainly from the intel where, the e1000 driver in Windows have many bugs and no longer supported by Intel.
Below VMware HCL link have the details on e1000 not support with 2012 server latest versions.