What is Whitelisting and Why is it Important?
Whitelisting is a simple process. It means you are creating a list of trusted senders. When you whitelist a domain, you're giving it special permission. This allows its emails to bypass spam filters.

Common Mailchimp Domains to Whitelist
There are a few key domains and IP addresses to whitelist. This is especially true if you are a business with a private email server. You should always check with your IT department first. Typically, a network firewall may block Mailchimp's traffic. These are some of the most common Mailchimp domains you or your recipients may need to whitelist:
How to Whitelist in Different Email Clients
The steps for whitelisting can change depending on the email service. However, the general idea is the same. For most email providers, you need to add the sender's address or domain to your safe sender list or contacts. For example, in Gmail, you can add a sender to your contacts. You can also move an email from the spam folder to the inbox. This teaches the filter to trust future emails from that sender. In Outlook, you can add an email address or a domain to the "Safe Senders and Domains" list. Similarly, Yahoo Mail lets you add a contact. In this way, you can easily ensure emails from Mailchimp are not blocked.