Mailing List

What Is a Mailing List?

A mailing list is a group of email addresses that allows a sender to distribute messages to multiple recipients using a single address.

Organizations and communities use mailing lists for newsletters, product updates, discussion groups, and internal communication. When someone sends an email to the list address, the mailing list software automatically forwards that message to all subscribers.

Common mailing list platforms include Mailman, Google Groups, and Listserv.

How Mailing Lists Handle Email

Mailing lists act as intermediaries in the email delivery process. When a message is sent to the list address, the list server receives it and then resends copies to each subscriber.

During this redistribution, the mailing list server may:

• Modify headers (e.g., changing “From” or adding “[List Name]” to the subject line).
• Add a footer with unsubscribe information or disclaimers.
• Resend the message from its own mail server instead of the original sender’s.

While these changes are normal, they often interfere with SPF, DKIM, and DMARC authentication, because the message now appears to come from a different source than the original.

Mailing Lists and Authentication Challenges

Mailing lists are one of the most common causes of legitimate DMARC failures. When a message passes through a mailing list:

• SPF typically fails, since the forwarding server isn’t listed in the sender’s SPF record.
• DKIM may also fail if the mailing list modifies the message body or headers after it was signed.
• DMARC can fail if neither SPF nor DKIM aligns with the original “From” domain.

To reduce these issues, some lists rewrite the “From” address to match the list’s domain or use ARC (Authenticated Received Chain) to preserve authentication results through forwarding.

Mailing Lists and DMARCeye

DMARCeye helps organizations understand how mailing lists affect their DMARC results.

By analyzing aggregate reports, DMARCeye identifies patterns of forwarded or redistributed mail, showing where authentication failures stem from legitimate mailing lists rather than malicious activity.

With this insight, administrators can adjust authentication settings, educate users, and adopt technologies like ARC to maintain both security and message deliverability in mailing list communications.