Sending an email to 14,000 customers is going to put your site into a world-of-hurt with your hosting provider. Better to use a bulk-mailing service like MailChimp or Constant Contact.
Provider allows 600 emails per an hour, so it can be done in a week.
Is it possible to select 599 addresses at ones in Zen Cart?
Or better way is somehow export all emails into spreadsheet and copy and paste 559 at a time?
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