returns some or returns error? did you give the api access permissions to those accounts?
make sure to check this official document.
The documentation says you can get up to only 1000 emails at once. And from permissions section, it seems only possible to get all emails from within an application given the permission Mail.ReadBasic.All
even for work account.
I don't have a work account thus I tested sending an email to myself on my personal account and tested the query on graph-explorer test page here. The first 2 results are those freshly received and freshly sent ones. with this I will say a work and personal/family accounts are no different on getting emails since you said you can get both received and sent mails from a work account.
so in short, you can get up to 1000 emails unless you use an application with permission to read all but with limited properties because Mail.ReadBasic
allows the app to read email in the signed-in user's mailbox except body, previewBody, attachments and any extended properties, and hence I deduce Mail.ReadBasic.All
does the same