Summary
For email deliverability, the use of hyphens in 'From' names and subdomains is handled differently based on their function. In the 'From' name, hyphens are widely accepted and can enhance readability or branding, as this is a flexible display field not constrained by strict domain naming rules. Conversely, hyphens are permitted in subdomains and other domain labels, following specific DNS regulations outlined in RFCs. These rules dictate that hyphens can be used within a label but must not appear at the beginning or end of any segment, nor adjacent to a dot or another hyphen. Adhering to these technical standards is crucial for valid domain resolution and successful email delivery.
Key findings
- From Name Flexibility: Hyphens are fully permissible and often beneficial in email 'From' names, which are display fields designed for flexibility, improved readability, and branding, not subject to the rigid rules of email addresses or domains.
- Subdomain Permissibility: Hyphens are allowed in subdomains and other domain name labels, according to established DNS standards like RFC 1035 and 1123. This is a common practice for organizing sending infrastructure.
- Strict DNS Rules for Subdomains: For subdomains, hyphens cannot be the first or last character of any label or segment. They also cannot be adjacent to a dot or another hyphen within the domain name structure.
- Deliverability Impact: Using hyphens in subdomains correctly, in compliance with DNS rules, supports valid domain resolution and successful email delivery. Non-compliant subdomains are considered invalid, directly preventing email from being sent or received.
Key considerations
- RFC Compliance is Critical: Ensure subdomains strictly adhere to RFC 1035 and 1123 to maintain validity and prevent deliverability issues, specifically regarding hyphen placement, as hyphens cannot be the first or last character of a label.
- Avoid 'Cousin Domains': Steer clear of domains that closely resemble yours but incorporate dashes, as they are often associated with spam or phishing attempts and can damage sender reputation. Instead, use proper, delegated subdomains.
- Clarity Over Complexity for 'From' Names: While flexible, ensure 'From' names with hyphens remain clear, recognizable, and align with your brand for optimal recipient identification and trust.
- Only Hyphens Allowed: Only standard hyphens (-) are permitted in domain names and subdomains; other dash types, such as em dashes or en dashes, are strictly forbidden and will render the domain invalid, preventing email delivery.
What email marketers say
13 marketer opinions
When considering the use of hyphens in email 'From' names and subdomains, it is important to distinguish between display fields and technical domain structures. In the 'From' name, which functions as a flexible display field, hyphens are widely accepted and can enhance readability or support branding efforts. Conversely, for subdomains and other parts of the domain name, hyphens are permitted but must strictly adhere to specific DNS regulations. These rules dictate that hyphens can appear within a domain label but not at its beginning or end, nor adjacent to dots or other hyphens. Proper adherence to these technical standards is essential not only for valid domain resolution but also for ensuring successful email delivery and maintaining sender trust.
Key opinions
- Flexible From Names: Hyphens are fully acceptable in email 'From' names, which serve as flexible display fields. Their use can significantly boost readability and align with branding, as these names are not subject to the rigid character rules of email addresses or domains.
- Subdomain Hyphen Rules: While permissible in subdomains and other domain name components, hyphens must strictly adhere to DNS rules, which mandate they cannot be positioned at the beginning or end of any segment, nor adjacent to a dot or another hyphen.
- Enhancing Readability: For 'From' names, hyphens can significantly improve clarity and recipient recognition, particularly when used to separate words or elements within a longer brand name, without causing technical issues.
- Supporting Infrastructure: Hyphens are frequently incorporated into subdomains for the strategic organization of sending infrastructure or for branding purposes, provided they consistently meet standard DNS naming conventions to ensure deliverability.
Key considerations
- Prioritize clear and recognizable 'From' names: Even with the flexibility of using hyphens, always ensure the display name remains easy for recipients to identify and aligns with your brand, building immediate trust.
- Strictly adhere to DNS rules for subdomains: Any subdomains incorporating hyphens must rigorously follow DNS naming standards. Non-compliance, such as incorrect hyphen placement, can invalidate the domain and lead to email delivery failures.
- Beware of 'cousin domains': Domains that feature dashes to closely resemble your legitimate domain are often linked to spam or phishing activities. Always opt for properly delegated subdomains to maintain sender reputation and recipient trust, rather than risking association with deceptive practices.
- Understand the deliverability impact: Accurate placement of hyphens in subdomains is fundamental for valid domain resolution and ensuring emails reach their intended recipients. Deviations from DNS rules can result in the domain being deemed invalid, severely hindering email deliverability.
Marketer view
Email marketer from Email Geeks explains that using hyphens or dashes in the From name is generally acceptable, provided it aligns with branding and is recognizable. She notes that while less common in From/reply-to addresses (e.g., @domain-example.com), it could be permissible if the email resolves to a valid mailbox.
30 Jul 2021 - Email Geeks
Marketer view
Email marketer from Email Geeks explains that dashes are acceptable in hostnames (like subdomains) as long as they are not adjacent to a dot or another dash, or at the beginning. They are also permissible in the local part of an email address. He strongly advises against using "cousin domains," which often incorporate dashes, as they are frequently associated with spammers or phishers. Instead, he recommends using proper subdomains delegated by the client for better deliverability and trust.
8 Sep 2022 - Email Geeks
What the experts say
1 expert opinions
Email subdomains, as integral parts of domain names, are governed by stringent syntax rules, notably RFC 1035 and 1123. These regulations limit characters to letters, numbers, and standard hyphens. Crucially, hyphens are permissible only within the subdomain structure and cannot appear at the beginning or end of a subdomain. Any other form of dash, such as an em dash or en dash, is strictly prohibited. Failure to comply with these precise RFC specifications renders a subdomain invalid, directly impeding email deliverability.
Key opinions
- Strict Syntax for Subdomains: Email subdomains must adhere to the stringent syntax rules defined by RFC 1035 and 1123, which permit only letters, numbers, and hyphens.
- Hyphen Placement Restrictions: Within a subdomain, hyphens are allowed but cannot be placed at the very beginning or end of any segment, adhering to specific domain naming conventions.
- No Other Dash Types: Only standard hyphens (-) are permissible in subdomains; alternative dash types, such as em dashes or en dashes, are strictly prohibited and will render the subdomain invalid.
- Deliverability Consequence: Non-compliance with subdomain naming conventions, particularly regarding hyphen usage and character types, directly results in an invalid subdomain and prevents email delivery.
Key considerations
- Validate Subdomain Syntax: Always rigorously validate that your email subdomains strictly comply with RFC 1035 and 1123, as these precise syntax rules are non-negotiable for email deliverability.
- Correct Hyphen Placement: Be diligent about hyphen placement within subdomains; they must never be used at the beginning or end of the subdomain string, a common error that can invalidate your domain.
- Exclude Non-Standard Dashes: Strictly prohibit the use of any non-standard dashes, such as em dashes or en dashes, in your subdomains, as only the conventional hyphen (-) is recognized and accepted.
- Prioritize RFC Compliance: Recognize that strict adherence to RFCs for subdomain naming is paramount; non-compliance, even with minor errors, will result in an invalid subdomain and direct email delivery failure.
Expert view
Expert from Word to the Wise explains that email subdomains, as part of the domain name, must adhere to strict syntax rules defined by RFC 1035 and 1123. These rules allow only letters (a-z), numbers (0-9), and hyphens (-). Hyphens cannot be at the beginning or end of the subdomain. Other types of dashes, such as em dashes or en dashes, are not permitted. If a subdomain does not comply with these RFCs, it is considered invalid, which would prevent email delivery.
19 Jul 2022 - Word to the Wise
What the documentation says
4 technical articles
Across numerous authoritative sources including RFC 1035, AWS, Microsoft, and Cloudflare, there is consistent confirmation that hyphens are permissible within domain names and subdomains. However, this allowance comes with strict placement rules. Predominantly, hyphens must not appear at the beginning or end of any label segment. Additionally, a specific caveat exists for labels starting with 'xn--', where hyphens are forbidden at the third and fourth positions. Adhering to these precise technical standards is critical for ensuring the validity of your domain and the successful delivery of your emails.
Key findings
- Hyphens Allowed in Subdomains: Hyphens are permitted within domain names and subdomains, a standard specified by RFC 1035 and supported by major service providers like AWS, Microsoft, and Cloudflare.
- Position Restrictions Apply: A universal rule across documentation is that hyphens cannot appear at the beginning or end of any label or segment within a domain name.
- Specific 'xn--' Rule: AWS documentation notes an additional restriction where hyphens are not allowed at the third and fourth positions if a label begins with 'xn--'.
- Consensus on Standards: Various authoritative sources consistently reiterate the same rules for hyphen usage in domain labels, confirming a widely accepted technical standard.
Key considerations
- Strictly Follow RFC 1035: Adhere rigorously to RFC 1035 and related DNS standards for hyphen placement in domain names and subdomains, as non-compliance leads to an invalid domain.
- Validate Hyphen Position: Ensure hyphens are never the first or last character within any segment of your subdomain to maintain technical validity.
- Check Special Cases: Be aware of specific restrictions, such as hyphens not being allowed at the third and fourth positions in labels starting with 'xn--'.
- Prioritize Deliverability: Correct hyphen usage in subdomains is fundamental for proper DNS resolution and email deliverability; errors can prevent emails from being sent or received.
Technical article
Documentation from RFC-Editor.org explains that according to RFC 1035, domain names, including subdomains, can contain letters, digits, and hyphens. However, they must begin and end with a letter or digit, and hyphens are not allowed at the beginning or end of a label.
7 Jul 2022 - RFC-Editor.org
Technical article
Documentation from AWS Documentation explains that when configuring DNS records, domain name labels (which include subdomains) can contain hyphens. However, a label cannot start or end with a hyphen, and hyphens are not allowed at the third and fourth positions if the label starts with 'xn--'.
8 Oct 2024 - AWS Documentation
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