White listing information for MailChimp delivery servers
If you're having trouble sending emails to a group of people at a company, it's probably because of their email firewall. It tends to look suspicious when multiple people at one company are getting the same email at the same time. You might send this page to their IT group and politely ask them to use the information here to whitelist our servers. This will hopefully prevent future delivery problems.
Keep in mind that the numbers below are not single IP addresses. In order to see which IP addresses each Classless Inter-Domain Routing (CIDR) contains, use a CIDR calculator like this one. For more information about IP addresses and ranges formats, try this resource.
For more information about how we keep abuse away from our system, and how we educate our users about proper email list management and etiquette, visit MailChimp's abuse desk page:
MailChimp is an email service provider that's been around since 2001. We've got millions of customers from all over the world—small business, Fortune 500s, nonprofits, schools, musicians, etc.—who use MailChimp to send more than 20 billion emails every month. Our servers deliver more than 1 billion newsletters every day, so we work very hard to keep abuse out of our system and maintain high overall deliverability. Nobody's perfect, but we like to think we try the hardest.