How to convert email to text in a Numbers spreadsheet?

I am trying to convert email addresses into plain text in a numbers spreadsheet. They were imported from a .csv file. I have formatted all of the cells in the sheet as text. But this one column of email addresses continues to open my Mail program when I try to edit a cell. It is maddening. I cannot find any obvious solutions in the Numbers program. Any help? It must be a simple fix that I am missing. Thanks!

[Re-Titled by Moderator]

Original Title: converting email to text in numbers