You could do this a couple different ways but for marketing I would just use one of the 5 custom fields under the customer screen and enter it there.  You can edit the label of those fields.  Those fields would be exportable on the customer list reports.

Thank you for that suggestion.  I have thought of that, but unfortunately, we are using all 5 custom fields.  Is it possible to add a 6th?

On the Contacts tab, you can add another contact that can have their own email address and phone number. I don't use it for that purpose, so I am not sure what will pull the info best. I just figured I would mention it since you can't add additional custom fields.

Thanks Gina.  Yes I tried that.  Unfortunately that field is not available when creating customer list reports.  Only the main contact's email is available to pull into the report/customer list.  It seems crazy to  me that there's a field for 2 phone numbers and a fax, but not a 2nd email.  

I feel the same way! Thankfully, I have only a very small handful of customers that I have a need for a 2nd email.