User753101303 posted
Hi,
Even with no filter at all you can't retrieve the actual message count ? If the server doesn't return the real count, my first thought would be a server side setting whose goal is to prevent massive downloads. This is a mail provider such as Google,
Outlook,etc ? If your own company you could perhaps ask the mail server admin...
Edit: for example at
https://superuser.com/questions/232044/gmail-pop3-limit someone have 398 messages but POP tells he have 250. It seems there is a setting to alllow downloasding all messages or those received from when an option is activated.