Can hyphens affect email deliverability?

While hyphens are technically allowed, their impact on deliverability can be indirect. If they make an email address harder to read or remember, they could lead to typos and bounces. More critically, using hyphens to create cousin domains that mimic legitimate brands will significantly harm your sender reputation and trigger spam filters.

Are there any rules for hyphen placement in subdomains?

Yes, subdomains must adhere to DNS (Domain Name System) rules. This means hyphens are allowed, but they cannot be at the beginning or end of a subdomain label (the part separated by dots), nor can there be two consecutive hyphens. For example, marketing-updates.example.com is valid, but e--mail.example.com is not.

Why do some forms reject hyphens in email addresses?

Some older or poorly configured web forms may not be fully compliant with modern email address RFCs and might use overly restrictive validation rules. This means they might flag technically valid email addresses containing hyphens as invalid, even though email providers would accept them. It's an issue with the form's programming, not the email address itself.

What is a 'cousin domain' and why should I avoid it?

A cousin domain is a domain that closely resembles a well-known brand's domain, often by adding a hyphen or making a slight misspelling (e.g., my-brand.com instead of mybrand.com). These are typically used for malicious purposes like phishing or spam, leading to severe negative implications for sender reputation and deliverability. You should always avoid using them.

Do hyphens in domain names affect SEO?

Generally, hyphens in domain names are considered neutral for SEO by search engines like Google . They view hyphens as word separators, similar to spaces. However, domain names without hyphens are often preferred for their ease of recall and typing. The primary impact on SEO comes more from the overall content, keywords, and quality of the website, rather than the presence of hyphens alone.

Are hyphens or dashes allowed in email From names and subdomains? - Technical - Email deliverability - Knowledge base

When setting up your email infrastructure, questions often arise about the characters you can and should use in your email addresses and domain names. One common query revolves around the use of hyphens, also known as dashes, in email From names and subdomains. It's a technical detail, but one that can significantly impact your deliverability and brand perception.

The short answer is yes, both email From names (the local part before the '@' symbol) and subdomains can technically include hyphens. However, the nuances of their placement and the varying interpretations by email service providers (ESPs) and internet service providers (ISPs) mean that there are important considerations for optimal email performance.

Understanding where hyphens are permissible and, more importantly, where they are advisable, is crucial for maintaining good sender reputation and ensuring your messages land in the inbox rather than the spam folder.

Hyphens in the local part of an email address

The local part of an email address refers to everything that comes before the '@' symbol, for example, john-doe in john-doe@example.com. According to RFC 5322, the specification for internet message format, a wide range of characters are permitted in this section, including hyphens.

While technically valid, practical challenges can arise. Some legacy systems or web forms may not be updated to fully comply with modern RFCs and might incorrectly reject email addresses containing hyphens. This isn't a problem with the email address itself, but rather with the validation logic of the particular system.

From a deliverability standpoint, hyphens in the local part generally have little direct impact, assuming the email provider itself supports them. Major providers like

Gmail and

Outlook widely accept them. The main concern is user experience and avoiding situations where a legitimate email address is deemed invalid by a recipient's system, as highlighted in various discussions on email address validation.

Email Part	Allowed Characters	Hyphen Rules
Local Part (before @)	Letters (a-z, A-Z), numbers (0-9), and various special characters including hyphens, periods, underscores, plus signs, etc. RFC 5322 provides full details.	Generally allowed anywhere, including at the end or start, although some providers may impose stricter rules.
Domain (after @)	Letters (a-z, A-Z), numbers (0-9), and hyphens (-).	Cannot start or end with a hyphen. Two consecutive hyphens are generally not allowed. RFC 1123 governs these rules.
Subdomain	Letters (a-z, A-Z), numbers (0-9), and hyphens (-).	Must follow the same rules as domain names: no leading/trailing hyphens, and no consecutive hyphens.

Hyphens in domain names and subdomains

When it comes to the domain part of an email address, including subdomains, the rules for hyphens are more stringent but still allow their use. Domain names and subdomains are governed by DNS (Domain Name System) rules, primarily defined in RFC 1123. These rules state that domain labels (the parts separated by dots) can contain letters, numbers, and hyphens.

However, there are specific restrictions on hyphen placement in domain labels. A hyphen cannot appear at the beginning or end of a domain label, nor can two hyphens appear consecutively. For example, my-domain.com is valid, but -mydomain.com or my--domain.com are not. These rules apply equally to subdomains.

Example of a valid subdomain with a hyphentext

email.my-brand.com

Using subdomains for email sending is a common and recommended practice for managing sender reputation and segmenting email streams. For instance, you might use marketing.your-domain.com for promotional emails and transactions.your-domain.com for transactional messages. Hyphens are perfectly acceptable within these subdomain labels as long as they follow the standard DNS naming conventions.

While technically sound, it's worth noting that some older advice suggested avoiding hyphens in domain names for ease of recall or verbal communication, as they can sometimes be forgotten or miscommunicated. However, for email deliverability specifically, a hyphenated subdomain that adheres to DNS rules is generally not an issue and is widely supported by mail servers.

Deliverability and reputation implications

The technical allowance of hyphens doesn't always translate directly to perfect email deliverability. While most systems can handle them, the perception of your domain and email address by ISPs and recipients is paramount. Consistency and clarity are key. A hyphenated domain that is difficult to read or remember might lead to typos, which in turn can increase bounces or even trigger spam traps, impacting your domain reputation.

One significant concern is the creation of cousin domains, also known as typosquatting domains. These are domains that are very similar to a legitimate brand's domain, often by adding a hyphen or a slight misspelling. Spammers and phishers frequently use such domains to trick recipients, leading to these domains (and any associated email addresses) being heavily scrutinized and often placed on email blocklists (or blacklists).

Safe hyphen usage

Readability: Using hyphens to separate words in a long domain or subdomain, like email-updates.yourcompany.com, improves clarity.
Brand consistency: If your primary brand name already uses hyphens (e.g., my-brand.com), using them in subdomains maintains a consistent identity.
Segmentation: Utilizing specific, hyphenated subdomains for different email types (e.g., news-alerts.example.com) can help manage sender reputation.

Risky cousin domains

Typosquatting: Creating domains like my-brandcompany.com instead of mybrandcompany.com to trick users.
Spam association: Cousin domains are often used by spammers, causing legitimate emails from similar-looking domains to be caught by email blocklists (blacklists).
Security bypass: Attempting to use a cousin domain to avoid a client's security enforcement, for example with DMARC policies, is risky and can lead to delivery failures.

To ensure strong deliverability when using subdomains (whether hyphenated or not), robust email authentication protocols like SPF, DKIM, and DMARC are essential. These records prove that your emails are legitimate and authorized to be sent from your domain, helping to counteract any potential negative perception, even if your domain name happens to contain hyphens.

Avoid cousin domains

Creating or using domains that are intentionally close to established brands or popular websites, especially with the addition of hyphens to mimic existing names (e.g., brand-name.com when the actual brand is brandname.com), is highly risky. This practice is often associated with phishing and spam activities, leading to immediate negative trust signals from ISPs and significantly increasing the likelihood of your emails being blocked or landing in the spam folder.

Views from the trenches

Best practices

Use hyphens to enhance readability in long domain or subdomain names, ensuring they don't appear at the beginning or end of labels, or consecutively.

Always align your email sending practices with your brand's official domain and naming conventions for consistency and recipient trust.

Regularly monitor your domain's health and deliverability using tools to quickly identify and address any issues related to character usage or blocklist status.

Implement strong email authentication (SPF, DKIM, DMARC) for all sending domains, including subdomains, to validate legitimacy and improve inbox placement.

Common pitfalls

Using hyphens incorrectly (e.g., at the start/end of a label or two consecutively) can lead to invalid domain names and email delivery failures.

Creating 'cousin domains' with hyphens that closely resemble legitimate brands can trigger spam filters and result in your emails being marked as suspicious or blocked.

Overlooking the impact of hyphenated domains on verbal communication and memorability, which might lead to recipient confusion or incorrect typing of email addresses.

Failing to set up proper email authentication for all subdomains, leaving them vulnerable to spoofing and reputation damage.

Expert tips

Opt for subdomains (e.g., 'email.yourdomain.com') over entirely new, hyphenated domains to maintain strong brand alignment and leverage your primary domain's reputation.

Prioritize simple, memorable email addresses and domain names where possible, even if complex hyphenation is technically allowed, to improve user experience.

Conduct thorough testing of email addresses and sending domains across various email providers to ensure consistent deliverability and address any unexpected rejections.

Leverage DMARC reporting to gain insights into how your domain is perceived by email receivers, which can help in identifying and mitigating issues related to domain naming.

Marketer view

Marketer from Email Geeks says senders sometimes use hyphens in From names, and it seems acceptable if consistent with branding and if the email address is valid.

2019-02-18 - Email Geeks

Expert view

Expert from Email Geeks says dashes are acceptable in hostnames, provided they are not placed next to a dot, another dash, or at the beginning.

2019-02-19 - Email Geeks

Final thoughts on naming conventions

In summary, hyphens are allowed in both the local part of an email address and within subdomain labels. For the local part, while technically flexible, practical limitations from some systems might make simpler addresses preferable. For domains and subdomains, strict DNS rules apply, meaning hyphens cannot be at the beginning or end of a label, nor can they be consecutive.

The key takeaway is to balance technical permissibility with practical deliverability considerations. Prioritize clarity and consistency for your recipients. Most importantly, always avoid creating 'cousin domains' with hyphens that could be mistaken for legitimate brands, as this practice is highly detrimental to sender reputation and can lead to immediate blacklisting (or blocklisting).

When in doubt, stick to simple, well-defined subdomains for your email sending, and ensure all your domains are properly authenticated. This approach will help you maintain strong deliverability and build trust with both ISPs and your audience.