I have an Excel spreadsheet with data which lists email addresses of people (group one) - say column A and email addressees of another group (B) - say Column B. Some of the email addresses appear on both lists.

IS there an easy way to send an email to an address which appears in Column A but does not appear in Column B - because of the way that data is presented the 'duplicate' email address will not appear in the same row in both columns.