Outlook notification subscription using Azure Webhook Domain Not Found - azure

Question

I am working on Creating a push notification for inbox messages to be sent to my azure webhook.
I have been following the documentation as a reference. Till now I have been able to create and register my app using the Azure app registration. I got the client_id and client_secret accordingly.
Shared below are the postman requests I made to first get the access code and then access_token and refresh_token from the Oauth authorization endpoints -
Getting the access code -
Endpoint - https://login.microsoftonline.com/{tenant}/oauth2/authorize
Authorization Type – Oauth 2.0
Headers –
Content Type: application/x-www-form-urlencoded
Body –
response_type: code
client_id: myClientId
redirect_uri: https://app.getpostman.com/oauth2/callback
response_mode: query
scope: https://outlook.office.com/mail.read
Getting the access_token -
Endpoint –
https://login.microsoftonline.com/{tenant}/oauth2/token
Authorization Type – Oauth 2.0
Headers –
Content Type: application/x-www-form-urlencoded
Body –
code: **********access_code***************
client_id: myClientId
scope: https://outlook.office.com/mail.read
grant_type: authorization_code
client_secret: *********client_secret*********
redirect_uri: https://app.getpostman.com/oauth2/callback
resource: myClientId
Now, as mentioned in the documentation, I am posting the following request for creating the subscription (using Fiddler) -
Endpoint –
https://outlook.office.com/api/v2.0/me/subscriptions
Headers –
Authorization: Bearer access_token_got_in_the_response_above
Content Type: application/json
Body –
#odata.type: #Microsoft.OutlookServices.PushSubscription
Resource: https://outlook.office.com/api/v2.0/me/mailfolders('inbox')/messages
NotificationURL: https://myAzureFunctionApp.azurewebsites.net/api/HttpNotificationHandler
ChangeType: authorization_code
The problem is that the response I am getting is a 404 Not Found. More specifically, X-CasErrorCode: DomainNotFound. I have double checked to make sure there are no typos in any specification.
To give some more Info, I had previously tried this and was successful in creating the subscription for my personal hotmail account. The user I am stuck with has been added to the Azure Active Directory as a guest user under the same tenant my app has been registered.
UPDATE
Here are some more questions that might be useful -
The email address is say email1#contoso.com, and the tenant is ABCcontoso.onmicrosoft.com. Will it make any difference?
The user is not added to the user group using this application in the Azure Active Directory app registration section, the only user shown is the admin who had registered the app. Is this required?
The app was registered on the Microsoft App Registration Portal. But it is reflected in the Azure Active Directory under the tenant. So, is hitting the OAuth2 v1.0 endpoint correct?
What should be the endpoint for creating a notification subscription for a work/organization account having office 365 subscription? The current endpoint https://outlook.office.com/api/v2.0/me/subscriptions uses v2.0, but the token provided is by v1.0 endpoint (if I understand it correctly).
Any help is appreciated.