Summary
Understanding the precise structure of a valid email address is crucial for maintaining a clean email list and ensuring high deliverability. Email validation goes beyond a simple syntax check, involving various layers of verification to confirm not just proper formatting but also the address's existence and active status. This process helps to reduce bounce rates and protect your sender reputation by preventing messages from being sent to non-existent or malformed addresses. Implementing robust validation practices at the point of data capture and regularly cleaning your lists can significantly improve your email marketing outcomes.
Key findings
- Syntactic validity: Many email addresses might appear malformed but are actually syntactically valid according to RFCs (Request for Comments). This means they follow the established rules for characters and structure, even if they're undeliverable.
- Plus addressing: Email addresses with a '+' symbol (e.g., example+tag@domain.com) are valid and commonly used for filtering or tracking purposes, routing to the primary inbox.
- Internationalized domain names (IDNs): Modern email systems support Unicode characters in domain names and Top-Level Domains (TLDs), broadening the definition of a valid email address beyond purely alphabetic TLDs specified in older RFCs.
- Beyond syntax: While syntax is foundational, true validation involves checking for domain existence and MX records, and even attempting an SMTP connection to verify the user's presence.
Key considerations
- Robust validation methods: Relying solely on basic regex for email validation can be insufficient due to the complexity and evolving nature of email address formats. More comprehensive methods are needed.
- Deliverability versus validity: An email address can be syntactically valid but still undeliverable (e.g., belonging to a non-existent user or an inactive domain). Focus on both aspects for effective email marketing.
- Prevention at signup: Implement email validation at the point of signup to prevent malformed or invalid addresses from entering your list. This reduces future deliverability issues and spam trap hits. Learn more about how to validate email addresses.
- Regular list cleaning: Periodically clean your email lists to remove old, invalid, or risky addresses. Even initially valid addresses can become invalid over time.
What email marketers say
Email marketers often approach validation with a pragmatic mindset, balancing strict technical adherence with the practical realities of data collection and deliverability. Their primary goal is to ensure that emails reach legitimate inboxes, avoiding bounces and negative impacts on sender reputation. While acknowledging the complexity of email address standards, marketers seek effective, often automated, solutions to maintain list hygiene and campaign performance.
Key opinions
- Practical validation needs: Marketers emphasize the need for validation methods that can identify and filter out poorly formed or undeliverable email accounts effectively, especially when importing large lists.
- Leveraging special characters: The ability to use '+' in email addresses for creating variations (e.g., for newsletters or different sign-ups) is seen as a valuable feature for tracking and organization, as these variations route to the same primary inbox.
- Concern over TLD proliferation: Some marketers express a general apprehension about the rapid and extensive expansion of generic Top-Level Domains, noting the added complexity this brings to validation and domain management.
- Syntactic validity vs. deliverability: There's a common understanding that an email address can adhere to syntax rules but still be undeliverable in practice, requiring more than just a basic format check.
Key considerations
- Automated validation tools: Employing automated email validation tools is essential for handling large volumes of addresses and catching common errors or malicious inputs.
- Preventing bad signups: Marketers should prioritize validation at the point of subscription or data entry to prevent malformed or fake email addresses from polluting their lists and impacting sender reputation. For more detail, refer to strategies for email list validation.
- Understanding false positives: Awareness of cases where valid addresses might be flagged (e.g., due to unusual but RFC-compliant syntax) is important to avoid excluding legitimate subscribers.
- Impact on deliverability: Unvalidated lists can lead to high bounce rates, which negatively impacts email deliverability and potentially leads to blacklisting, making comprehensive validation a critical investment.
Marketer view
Marketer from Email Geeks asks about methods to validate email account structures to prevent importing malformed addresses, providing examples of problematic inputs.
Marketer view
Marketer from OneSignal explains that email validation involves checking for proper formatting and adherence to standard syntax rules, which is crucial for overall deliverability.
What the experts say
Experts in email deliverability and internet standards offer a deeper, more nuanced perspective on email address validation. They understand the intricacies of RFCs and the historical evolution of email syntax, recognizing that what is technically 'valid' according to specification might not always be 'deliverable' in practice. Their insights often highlight the challenges of precise regex parsing, the impact of internationalization, and the ongoing debate surrounding email address standards.
Key opinions
- Syntax vs. deliverability: Experts confirm that many seemingly problematic email addresses are indeed syntactically valid, even if they are ultimately undeliverable.
- Evolving TLD rules: While older RFCs specified alphabetic TLDs, modern standards and internationalized domain names (IDNs) allow for a broader range of characters, including Unicode, in the domain part of an email address.
- Plus addressing validity: The use of '+' for sub-addressing (e.g., user+alias@domain.com) is a perfectly valid part of email addressing.
- Complexity of RFCs: The rules governing email address syntax, particularly in RFCs, are highly complex and have evolved, leading to ongoing debate about precise interpretations and implementation.
Key considerations
- Beyond regex: Simple regular expressions (regex) are often insufficient for truly comprehensive email validation due to the vast and sometimes counter-intuitive allowances in RFCs. Proper validation might require checking domain records (MX records) and even attempting connection.
- RFC interpretation: Understanding the relevant RFCs (e.g., RFC 5322, RFC 1035 for domain names, and IDN-related RFCs) is key to deep email validation, but applying them strictly can be challenging.
- Internationalization impact: The move towards internationalized domain names means validation systems must accommodate a wider range of character sets and structures, complicating the process.
- Maintaining deliverability: While a strict syntactic check is a starting point, achieving high deliverability requires validation that goes further to confirm an address is not only valid in format but also actively receives mail.
Expert view
Expert from Email Geeks points out that most email addresses, even those that appear undeliverable, are often syntactically valid according to email standards.
Expert view
Expert from Word to the Wise explains that email validation is far more complex than a simple regex, emphasizing the many legitimate edge cases that a basic format check might miss.
What the documentation says
Official documentation, primarily through RFCs from the IETF, provides the foundational rules for email address structure. These documents detail the allowed characters, segments, and overall format of email addresses. However, the sheer volume and evolution of these specifications mean that a strict, literal interpretation can be complex and sometimes misaligned with practical, real-world usage, especially with the introduction of internationalized domain names.
Key findings
- RFC 5322: This RFC specifies the general format of internet messages, including the syntax for email addresses. It defines the local part (before '@') and the domain part (after '@').
- Domain name rules: Early RFCs, like RFC 1123, stated that Top-Level Domain (TLD) names should be alphabetic. However, this has been superseded by developments in internationalization.
- Internationalized domain names (IDNs): Newer standards support the use of non-ASCII characters (Unicode) in domain names, allowing for TLDs in various languages (e.g., .中国). This expands what constitutes a valid domain part of an email address.
- Sub-addressing: The use of the '+' character within the local part of an email address for sub-addressing (e.g., username+tag@example.com) is a valid feature supported by many email providers.
Key considerations
- RFC complexity: The full RFC specification for email addresses is highly complex, making it difficult to create a single regular expression that captures all valid cases without also allowing some invalid ones.
- Practical versus theoretical validation: While RFCs define theoretical validity, practical email validation often needs to consider what mail servers actually accept and deliver. See our article on what RFC 5322 says versus what actually works.
- Keeping up with standards: Email address standards continue to evolve, particularly with internationalization, requiring validation systems to be updated regularly to remain accurate.
- Impact on input forms: Developers building email input forms must decide on a balance between strict RFC compliance and user-friendliness, to avoid rejecting valid but unusual email addresses.
Technical article
Documentation from IETF.org references RFC 1123, which states that top-level domain names are expected to be alphabetic, highlighting an older standard that has since evolved.
Technical article
Documentation from Emailregex.com provides a regular expression touted as being 99.99% effective for validating email addresses, acknowledging the difficulty of creating a perfectly comprehensive one.
Related resources
14 resources
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