Office 365 - Mailing List Subscriptions After Changing Primary Address
Many mailing lists can only receive messages from email addresses that are subscribed to them. Once your primary email address changes, you will still receive emails addressed to the list via the address that is subscribed. However, you will not be able to send to the list from your new primary address. If you are subscribed to list(s) that are not managed through WiscList, you may need to change your address for those lists manually.
Thankfully, there is a Global Address Change tool built into WiscList which will replace all of your WiscList subscriptions with your new primary address. See this document for details:
You will need to update subscriptions to non-WiscList mailing lists manually.