Summary
Experts, marketers, and technical documentation agree that using subdomains for outbound email delivery can improve deliverability by isolating sender reputation and separating different email streams (transactional, marketing). Proper authentication (SPF, DKIM, DMARC) is crucial for each subdomain. Avoid sending unsolicited bulk emails, ensure permission for email addresses, warm up new subdomains slowly, and monitor subdomain reputation regularly.
Key findings
- Reputation Isolation: Subdomains protect primary domain reputation by isolating different email streams.
- Email Stream Separation: Separating transactional and marketing emails onto different subdomains improves deliverability.
- Authentication is Key: Proper configuration of SPF, DKIM, and DMARC for each subdomain is crucial.
- Avoid Spam: Sending unsolicited bulk emails harms reputation and deliverability.
Key considerations
- Permission & Data: Ensure you have proper permission to use email addresses and that data handling complies with regulations.
- Warming Up: Slowly warm up new subdomains to build a positive sender reputation.
- Reputation Monitoring: Monitor subdomain reputation metrics (deliverability, bounce rates, spam complaints) regularly.
- List Quality: If your list is new or of questionable quality, subdomains are essential
What email marketers say
13 marketer opinions
Using subdomains for outbound email delivery can improve deliverability by isolating sender reputation. Segmenting email types (transactional, marketing) onto separate subdomains prevents deliverability issues in one area from affecting others. Warming up new subdomains slowly and monitoring their reputation are crucial. Sending unsolicited bulk emails, regardless of the list source, can harm your reputation. Obtaining proper permission for email addresses and adhering to data privacy regulations is essential.
Key opinions
- Reputation Isolation: Subdomains isolate sender reputation, protecting core domains from marketing campaign issues.
- Segmentation Benefits: Segmenting email types improves deliverability by maintaining distinct sender reputations.
- Warming Up: Gradually warming up new subdomains is important to building a positive reputation with ISPs.
- Email Type and Content: Spam is unsolicited bulk email and should be avoided. To not be spam, email can either be solicited & bulk, or unsolicited & not bulk.
Key considerations
- Data Acquisition: Avoid sending emails to lists acquired from sources without explicit consent, as this is often considered spam.
- PII Permission: Ensure you have proper permission to use Personal Identifiable Information (PII) and to send emails to recipients.
- Reputation Monitoring: Regularly monitor subdomain reputation metrics like deliverability, bounce rates, and spam complaints.
- Legal Compliance: Be aware of data privacy regulations (like GDPR) and ensure your email practices comply with legal requirements.
Marketer view
Email marketer from SendGrid explains that using subdomains to separate different types of email traffic (transactional vs. marketing) is beneficial. This prevents a poor reputation for marketing emails from affecting transactional emails, which are critical for user experience.
16 Aug 2024 - SendGrid
Marketer view
Email marketer from Litmus recommends using subdomains to separate email streams, allowing for better control over sender reputation and minimizing the impact of marketing campaigns on critical transactional emails.
15 Sep 2023 - Litmus
What the experts say
3 expert opinions
Experts agree that using subdomains for different email streams is generally a good practice for managing reputation and improving deliverability. Setting up proper authentication (SPF, DKIM, DMARC) for each subdomain is crucial to avoid being flagged as spam.
Key opinions
- Good Practice: Using subdomains for different email streams is a common and generally good practice.
- Reputation Management: Subdomains help separate email streams and manage reputation, protecting core domain reputation.
Key considerations
- Authentication: Properly configure authentication (SPF, DKIM, DMARC) for each subdomain to ensure deliverability.
Expert view
Expert from Word to the Wise responds that when setting up subdomains for email, it’s crucial to properly configure authentication (SPF, DKIM, DMARC) for each subdomain to ensure deliverability and avoid being flagged as spam.
6 May 2025 - Word to the Wise
Expert view
Expert from Email Geeks shares that using subdomains for different mail streams is common and generally good practice.
25 Apr 2022 - Email Geeks
What the documentation says
4 technical articles
Technical documentation consistently emphasizes the importance of properly configuring DNS records, including SPF and DKIM, for each subdomain used for outbound email. This authentication process is crucial for improving deliverability and preventing emails from being marked as spam or used for spoofing.
Key findings
- DNS Records: Setting up subdomains requires creating new DNS records specifically for the subdomain, including SPF and DKIM records.
- SPF Configuration: SPF records need to be specifically configured for each subdomain sending email; incorrect SPF increases spam likelihood.
- DKIM Implementation: Implementing DKIM involves generating a new key pair and updating DNS records to verify the email sender.
- Authentication Importance: Proper email authentication (SPF, DKIM, DMARC) is essential for deliverability and preventing spoofing.
Key considerations
- Authentication Setup: Ensure proper SPF, DKIM, and DMARC records are configured for each subdomain to maximize deliverability and security.
- DNS Updates: When setting up a new subdomain or changing email providers, remember to update the DNS records accordingly.
Technical article
Documentation from RFC explains that SPF records need to be specifically configured for each subdomain that sends email. Without a correct SPF record, emails from the subdomain are more likely to be marked as spam.
26 Jun 2021 - RFC
Technical article
Documentation from Microsoft emphasizes the importance of proper email authentication (SPF, DKIM, DMARC) for all subdomains used for email sending to ensure deliverability and prevent spoofing.
3 Mar 2024 - Microsoft
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