Why do companies use cousin domains for email campaigns?
Summary
What email marketers say9Marketer opinions
Email marketer from Mailjet.com explains that some companies use different domains or subdomains to segment email streams (transactional, marketing, etc.) to help manage reputation and prevent issues with one type of email affecting the deliverability of others.
Email marketer from Gmass.co explains that some companies use cousin domains to bypass sending limits imposed by email service providers. This allows them to send more emails per day/month than they could with a single domain.
Email marketer from Reddit explains that some companies find it easier to manage and isolate sending infrastructure by using different domains, rather than dealing with the complexities of subdomains and DNS management on their primary domain.
Email marketer from Email on Acid shares that companies might use distinct domains for specific campaigns to streamline tracking and analytics. Separating campaigns at the domain level allows for clearer reporting on performance metrics.
Email marketer from StackExchange responds that companies use cousin domains as a quick fix to avoid the work of fixing their primary domain's reputation or when they lack control over their main domain's DNS records.
Email marketer from SparkPost.com shares that companies might use separate domains to protect their primary brand domain's reputation. If a marketing campaign damages the sending reputation, it won't impact emails sent from the main domain (e.g., transactional emails).
Email marketer from EmailOctopus.com states that another reason to use multiple domains is for better brand perception. Sending from different domains can help tailor the sender address to the email content, which can improve open rates and engagement.
Email marketer from Reddit shares that companies use cousin domains to maintain a separate reputation for marketing emails from their transactional emails to safeguard company email deliverability.
Email marketer from Campaign Monitor shares that some businesses use multiple domains to represent different product lines, customer segments, or geographic regions. This helps them tailor their messaging and branding to specific audiences.
What the experts say4Expert opinions
Expert from Spam Resource explains that using cousin domains doesn't solve underlying sending problems and that inbox providers often group them together for reputation purposes anyway. It can also damage your reputation as it is a sign that you are trying to circumvent spam filters.
Expert from Word to the Wise explains that senders use cousin domains for various reasons, including internal politics, the desire to send mail without impacting the reputation of their primary domain, and a lack of understanding about the impact of their sending behavior. They also mention that marketing departments sometimes want more control than IT is willing to give them.
Expert from Email Geeks states that what Facebook is doing is called "cousin domains" and advises against it.
Expert from Email Geeks shares multiple reasons for using cousin domains, including senders being idiots, ESPs finding it easier to sell new domains, conflicting motivations between IT security and marketing, and evading internal company rules.
What the documentation says4Technical articles
Documentation from Google suggests that using a dedicated domain for sending bulk emails can help protect the reputation of your main domain. This also helps to ensure that important transactional emails are delivered reliably.
Documentation from dmarc.org explains that subdomains can be helpful to isolate sending streams, and to test DMARC policies without affecting mail flow for your primary domains.
Documentation from rfc-editor.org (RFC 7208) explains that while SPF authenticates the MAIL FROM identity, organizations may choose to use different domains for different classes of mail to ease management, and to isolate the reputation of different mail streams (marketing vs transactional).
Documentation from Microsoft.com explains that organizations often use multiple domains to reflect different parts of their business, or to simplify email addresses for users, and that you can add and validate multiple domains in Exchange Online.