What is a seed list and how to build one
If you want to know what happens in the inbox when you send a campaign, test it out for yourself with a seed list. It's a separate list of email addresses you or your team own that you can send your campaigns to before sending to your subscribers.
So rather than sending a test message, you can send a campaign to your seed list. It'll give you the most accurate overview of the deliverability and inbox placement, and will allow you to preview the message in different email clients.
You can build one by creating a new list and adding a couple of your own email addresses to it, preferably across different email clients (Gmail, Hotmail, a private domain etc.). Then, when creating a campaign, you can select your seed list as the recipient.
Once you've sent your campaign to the Seed list, you can duplicate it and send it to any other list.