How many subdomains should I use per dedicated IP address for email sending?
Summary
What email marketers say8Marketer opinions
Email marketer from Mailjet shares that using subdomains for different types of email (transactional, marketing, etc.) helps to isolate reputation and prevent one type of email from negatively impacting the deliverability of another.
Email marketer from Email Marketing Forum explains that if you have very low volume, consider using a single subdomain. Spreading volume across multiple subdomains with minimal traffic can negatively impact deliverability.
Email marketer from Email on Acid shares that using subdomains is about isolating reputation. If one subdomain gets a bad reputation (high spam complaints), it won't affect the deliverability of other subdomains.
Email marketer from GlockApps explains that using a sending subdomain helps increase deliverability. Sender reputation is tied to the sending subdomain rather than the main domain.
Email marketer from Email Geeks shares that the volume depends on what is being sent on each subdomain and dedicated IP. Adding that 1.5 million emails per month can withstand a dedicated IP and pay close attention to each stream per dedicated IP if you get multiple.
Email marketer from Reddit shares that they use separate subdomains for transactional and marketing emails to keep their sender reputation clean and avoid deliverability issues.
Email marketer from Sender.net explains that using a sending subdomain is a best practice to protect your main domain’s reputation. This isolation ensures that deliverability issues on the subdomain won’t impact your primary domain's email.
Email marketer from Sendinblue shares that using a sending subdomain allows to manage sender reputation separately from the main domain. This approach ensures that marketing campaigns or transactional emails do not affect the main domain’s reputation.
What the experts say4Expert opinions
Expert from Email Geeks shares to warm up when moving to ensure a smooth transition. Very small amounts from the new IPs and gradually reduce volume from the shared until you’ve moved everything.
Expert from Email Geeks explains that a subdomain should be used for each distinct mail stream, irrespective of the number of dedicated IPs. He also mentions it depends if you're using subdomains for DKIM identifiers.
Expert from Word to the Wise explains that subdomains are crucial for deliverability. Utilizing separate subdomains based on sending purpose protects your primary domain’s reputation and ensures optimal deliverability.
Expert from Spam Resource explains that it depends on the email program, some email streams should be isolated to a subdomain. These can include marketing, transactional, and bulk emails, each using a distinct subdomain, to maintain reputation.
What the documentation says4Technical articles
Documentation from RFC explains that using subdomains makes it easier to manage DKIM keys. Every subdomain can have its own DKIM key, which allows greater control and better security.
Documentation from AWS explains that using multiple subdomains to differentiate email types improves deliverability by isolating sender reputation. They recommend aligning subdomains with specific use cases.
Documentation from SparkPost explains that delegating subdomains for email sending allows for easier management of DNS records and helps to improve deliverability by segmenting email traffic.
Documentation from Microsoft Learn explains that using subdomains helps to organize your email sending infrastructure and allows for more granular SPF records, improving deliverability.