Originially published on Medium on September 22, 2016.

The Problem

I get emails from lots of organizations that use MailChimp. How can I tell that they use MailChimp? Because their emails always start like this:

Sender <person=example.com@mail215.atl61.mcsv.net> on behalf of Sender <person@example.com>

I use Office 365 at work and usually browse email in Outlook. And every single MailChimp email I receive that way has a garbled From address just like above.

Because the email is sent by MailChimp’s servers, the From address usually includes the domain of that MailChimp server. This causes three problems:

1. It’s ugly.
2. I might think it’s spam.
3. I can never whitelist emails from your domain because it’s never your domain — it’s always a different MailChimp server!

This is fairly easy to fix. All you need to do are make a few DNS tweaks to your domain and your emails will no longer show this garbled mess in the From field in Outlook.

The Fix

All you need to do are add two DNS records.

Type:  CNAME
Host:  k1._domainkey.example.com
Value: dkim.mcsv.net

Type:  TXT
Host:  example.com
Value: v=spf1 include:servers.mcsv.net ?all

That’s it! Once you’ve added/modified these DNS records, your email addresses sent from MailChimp to Outlook clients will look just fine!

You may already have a TXT record that begins v=spf1, in which case you just need to add include:servers.mcsv.net to the list of domains already in that record.

The Explanation

When Outlook shows the garbled From address in the first place, it’s because it doesn’t know if it should trust the MailChimp server as a legitimate sender for your domain. DKIM and SPF records are designed to help email servers know who can or cannot legitimately send mail on behalf of a domain. With these records in place, emails will correctly display as Sender <person@example.com> because Outlook has a way to verify that MailChimp is authorized to send mail for the example.com domain.