An ESP is not going to allow you to import any list which is not confirmed. This means one of two things:
- You will have to send a confirmation email to each subscriber on the list and get them to confirm their subscription.
- They may (as we do) be able to test your list via compliance and if it has no issues, allow you to bypass the confirmation. With us, you can simply contact support for more information. But we do have strigent policies regarding this.