Outlook Classic - Can only sync up to 8k max emails into Inbox (Yahoo email account)?

I have Windows 10 Prof installed.

I'm trying to use Outlook to work with my Yahoo email account.

I used MS Outlook (new) first. It couldn't sync any emails from Yahoo server into Outlook's Inbox. 

I switched to Outlook Classic, and it slowly and finally synced about 8k emails into the Inbox in Outlook from my Yahoo email account.  This, however, is still only about 50% of the emails in my Yahoo webmail's Inbox.

I can't read any older Yahoo emails in Outlook Classic at the moment because of this issue.

Is there an upper limit in Outlook of how many mails can be synced to Outlook for a Yahoo email account? Is that a limit on the Outlook side, or from Yahoo server side?

Thanks.

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Update:

It seems this is happening to folders as well. Outlook Classic can only sync to around 8.8k max or so mails from Yahoo for each folder.  Windows 10 Pro.

PS:

I'm not able to try out the new Outlook yet, as it cannot even sync any mail from Yahoo into the Inbox at all.