If you're changing from a Constant Contact account over to Mailchimp, there are few things to keep in mind about lists that can streamline your transition.
Differences Between ESPs
In your Constant Contact* account, you'd only have one main list in the account, as a General Interest category. Additional lists are subsets of General Interest, so some subscribers may only be in General Interest and other subscribers may be in other lists as well as General Interest.
Each new Mailchimp list is like your General Interest list. When you move your list to Mailchimp, we'll move your Constant Contact sublists and segments into groups. Groups are the equivalent of your former "New Lists."
There is a limit of 60 groups for each list in Mailchimp.
What Do I Do?
Since Mailchimp recommends a different approach to list management, it's likely you'll be able to reduce the number of groups needed.
We recommend you break up your General Interest list into multiple lists in your Mailchimp account. If you exceed 60 groups, export your General Interest list from Constant Contact and open it in a spreadsheet application. Delete unnecessary list columns or consider a way to combine sublists into common groups. Remember that you can use Mailchimp's segmentation feature to further subdivide and target subscribers, if groups are insufficient.
*Constant Contact is a registered trademark of Constant Contact, Inc. All Constant Contact products and services that we mention are property of Constant Contact, Inc. We're not affiliated in any way with Constant Contact, Inc.