Email Hippo’s CORE email list validation service accepts files in CSV and TXT formats. Please make sure your file is in one of our accepted formats before attempting to upload. 


When you upload a file, CORE will scan it to determine how many unique emails are contained within the file. 


Email Hippo will not charge you for duplicate email addresses contained within the file. 


The file may be rejected if something unusual is detected. The following article will explain why this has happened: CORE error messages explained