Cannot publish an app – Sent Emails table

I am trying to expose data as a web service, table 8889 -SEnt Emails. HOwever, when I publish I get the following error messages:

Package validation failed due to the following error(s): API/sent_Email_ALL_SOD.APIPage.al (33,38) – Error AL0161: ‘”Message Id”‘ is inaccessible due to its protection level

Any way to fix this?