Need to delete 15,000 emails from inbox

Need to delete 15,000 emails from inbox

Hello, 
I am using Thunderbird client with Pop server connection.  I did not realize that I had to enable email delete on BOTH the client and server account.   One of my accounts ( anne.n@webeshoe.com) has over 15,000 emails in it.  I would like to delete all emails more than 14 days old.  I tried using the Zoho web email client but it only allows me to select 200 email messages at a time.  So I tried to use my Thunderbird client to re-download all the messages in the Zoho inbox and then tell the the server to delete them.   I deleted my popstate.dat file on my client and restarted Thunderbird
Unfortunately Thunderbird will only download about 355 messages and then says there are no more.  I downloads the most recent messages but then stops.

If I do delete a message on Thunderbird the message is removed from my Zoho inbox.   I just cannot figure out how to clear out the older messages.