Whether or not an organisation will want to use a Raiser's Edge Query versus a Raiser's Edge Export will be dependent upon their data setup and needs.
Use of Query is a bit less setup time (as use of Export would usually require both a Query and an Export). If you do not have many email addresses in Raiser's Edge or if all of the emails that you would like to integrate exist with a very specific coding, this may be sufficient.
Use of Export will provide additional options that can help an organisation to better select the email address that is most appropriate to migrate from Raiser's Edge into Mailchimp and it also gives options to help with removing deceased individuals and handling Head of Household processing.
After you've created your Query and you go to create your Export, you have the option in the Export to select how to address Head of Households, constituents marked deceased, inactive or no valid address. When used in conjunction with duplicate settings in Chimpegration, these fields can help you manage the information between your systems.
Additionally, you can use the criteria for the Phone Number to sort the email addresses (using the field that best meets your standards) and you can choose to ignore any email address already marked as "Do Not Contact."
The settings above will choose only one email address per constituent and they will exclude any that are marked "Do Not Contact" and the priority will be given to the most recently changed email address. You could also change the sort to give preference to the Primary email using the "Is Primary?" functionality or any of the other Order by options in the bottom right corner.