Import from access with fields that contain user email in office 365 list

I have a list of 5000 records that comes from an excel file. I have reorganised the file so all the data is clean and has the same order of the columns as in the Office 365 / Sharepoint list.

To simplify the Import, access is used with a linked table and the temporary table with the data from the excel file. The first 3 columns contains the user e-mail addresses. ( i can change if required). in the table that need to be exported.

The list in SharePoint, these columns are created as 'user' field, so they are linked to a user ( so we can see the presence, e-mail and details).

When i import, the process complains about conversion failure at the end and the 3 columns remain blank.

Do the users need to be part of the the site or is it globally.

Is there a specific syntax for the user name or do i miss something? i have tried with the usercode and e-mail.