Definition
A subdomain like mail.example.com is a separate part of your domain used for sending, isolating reputation and simplifying DNS.
Reputation is evaluated per subdomain, protecting your main domain.
Subdomains let you separate email streams so one campaign type does not threaten another. Each needs its own authentication and reputation management. This containment protects your main domain from a single problematic stream.
Why Send from a Subdomain
Separate marketing, transactional, and bulk sending.
SPF, DKIM, and DMARC can be scoped to it.
Why It Matters
Subdomains let you separate email streams so one campaign type does not threaten another. Understanding them makes reputation management simpler.
Best Practices
- Create a dedicated subdomain for marketing sends.
- Set up SPF, DKIM and DMARC for the subdomain.
- Warm and monitor it like any sending identity.
- Publish SPF, DKIM, and DMARC for the subdomain.
- Warm up and monitor its reputation separately.
- Keep the subdomain naming clear.
- Document which subdomains are authorised.
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Related Glossary Terms
Abuse Complaint
An abuse complaint is a report from a recipient who marks an email as spam, which negatively affects sender reputation and deliverability.
Alt Text
Alt text is the written alternative to an image in an email, displayed when images are blocked, slow to load, or consumed by screen readers.
AOL Mail for Email Marketers
AOL Mail is a legacy email provider with specific deliverability requirements and rendering quirks, now operating as part of the Yahoo+AOL network under shared infrastructure.
Email Authentication Protocols
Email authentication protocols are technical standards that verify the identity of an email sender, helping mailbox providers distinguish legitimate mail from spam and phishing.
BIMI
BIMI (Brand Indicators for Message Identification) is an email standard that allows brands to display their logo next to their emails in supported email clients. It requires DMARC enforcement at quarantine or reject policy.
Bounce Management
Bounce management is the process of handling emails that are rejected by mailbox providers, including classification, removal of bad addresses and protection of sender reputation.
Frequently Asked Questions
To isolate reputation and simplify DNS management. Subdomains let you separate email streams so one campaign type does not threaten another.
Yes, records apply per subdomain. Each needs its own authentication and reputation management.
Reputation is generally separate. This containment protects your main domain from a single problematic stream.
Something clear like mail.example.com. Subdomains let you separate email streams so one campaign type does not threaten another.
Yes, but each needs management. Each needs its own authentication and reputation management.