You first need to have a query built which contains the group of accounts you want to remove the email addresses for. As the accounts that need to be modified will vary from one situation to another, this solution will not cover how to create the query. One of the most common query solutions for this situation is to create a custom account query using the steps listed at How to create a query for specific accounts.

After you have created the query to find the accounts that you need to remove the email addresses for, you can run the following two mass updates to remove those addresses:

First we run a mass update to assign all of the accounts the same email address. This is necessary, as you are only able to mass remove data from a field if all accounts have the same information in that field:
  1. Click Management
  2. Click Mass Update
  3. Click Update Existing Personas
  4. Select the query that contains the group of accounts you need to remove email addresses for at the top of the page
  5. Select Primary Persona under Personas to Update. You may select 'The Specific Persona I Select' instead and then choose a Persona in the drop down menu (ex: Personal) if you wish to update a specific Persona for each account, rather than just the Primary Persona. 
  6. Select Assign under Update Type
  7. Type in a sample email address (ex: test@test.com) in the Email field; do not fill out any other fields on this page
  8. Click Next to preview the list of accounts
  9. Click Next to run the mass update on the Preview step
Now, we can run a second mass update to remove the email address from each of the accounts:
  1. Click Management
  2. Click Mass Update
  3. Click Update Existing Personas
  4. Select the query that contains the group of accounts you need to remove email addresses for at the top of the page
  5. Select the same option you did in step 5 in the first set of instructions regarding the Persona you want to update
  6.  Select Remove under Update Type
  7. Type in the same email address that you assigned to all of the accounts in the first mass update (ex: test@test.com) within the Email field; do not fill out any other fields
  8. Click Next to preview the list of accounts
  9. Click Next to run the mass update on the Preview step