See below different options so that Notes groups are provisioned in AD/Exchange with a second alias:
WORKAROUND 1:
Add the alias in the Notes group. Then run MNE operation "Export Notes Directory" and provision the group.
WORKAROUND 2:
From MNE, export the TSV file, modify the corresponding field for aliases and import the TSV file. Then provision de group.
WORKAROUND 3:
Add the "aliasdomainname.com" domain name in the MNE "Find Domains" section. Please be aware that every single object will have this domain name added as soon as the "Export Notes Directory" operation is run.
It is strongly recommended to test these workarounds on a test scenario prior to run them in production.