Why is it that I don't see any MassMailer Email Status-related list records?
The following fix may help fix the issue as there could be several other reasons. Please check the following if you are facing this issue.
One of the issues could be that you have an Organization-Wide Default set as Private for Lead, Contact, Account, and Campaign objects.
In order to fix this, you will have to create a public group ‘Massmailer’.
Search for “Public Group” in Quick Box.
Click on New
Name the Label and Group Name as ‘MassMailer’
Add “MassMailer Site Guest User”
Then you have to create Sharing Rule for the Objects which are Private
Sharing Settings--> Lead Sharing Rules --> New
Label Name: MassMailer
Select which records to be shared: All Internal User
Select the users to share with MassMailer
Once It is saved then we can see the Sharing Rule just like below-
This should resolve the issue. If not, we can certainly look into your Salesforce Org and help. Please contact our support team for further assistance.