How do I validate the structure of an email account and what are some valid email address examples?

Summary

Validating email addresses involves a multi-faceted approach, considering both syntax and deliverability. Experts and documentation sources agree that modern email syntax is complex, allowing for special and internationalized characters (Unicode). While regular expressions can check syntax, overly strict patterns are discouraged as they may reject valid addresses. A more reliable approach involves deliverability checks, such as sending confirmation emails and monitoring bounces. Email validation services offer comprehensive checks, including syntax, domain existence, mailbox existence, and spam trap detection. Marketers also highlight the importance of typo detection, plus addressing, and detecting disposable email addresses to maintain list quality and sender reputation.

Key findings

  • Syntax Complexity: Modern email address syntax is complex, with special and internationalized characters allowed.
  • Unicode Support: Full Unicode is allowed in the domain part of email addresses.
  • Regex Limitations: Overly strict regular expressions can reject valid email addresses.
  • Deliverability Focus: Focus on deliverability checks, such as sending test emails and monitoring bounces.
  • Comprehensive Services: Email validation services offer comprehensive checks, including syntax, domain, and mailbox existence.
  • Plus Addressing: Many services support plus addressing (e.g., yourname+keyword@example.com).
  • Typo Detection: Real-time typo detection improves email capture accuracy.
  • Disposable Addresses: Detecting disposable email addresses is important for list quality.
  • IETF Definition: IETF provides definitions of what a valid email should consist of.

Key considerations

  • Choose Validation Method: Select a validation method that balances syntax checking with deliverability concerns.
  • Regularly Clean Lists: Regularly validate and clean email lists to maintain sender reputation.
  • Consider Service Integration: Consider using a validation service that offers comprehensive checks.
  • Email Confirmation Process: Implement a confirmation email process to ensure email address ownership.
  • Internationalization: Ensure validation methods support internationalized domain names.

What email marketers say
10Marketer opinions

Validating email addresses involves ensuring they adhere to the correct structure and are deliverable. Techniques range from simple syntax checks using regular expressions to more sophisticated methods like sending confirmation emails and detecting disposable addresses. Valid email addresses can include alphanumeric and special characters, and many services support plus addressing (e.g., yourname+keyword@example.com). Real-time typo detection helps prevent errors during email capture. Email validation is crucial for maintaining a clean email list, improving deliverability, and protecting sender reputation. It helps prevent bounces, spam complaints, and blacklisting.

Key opinions

  • Plus Addressing: Many email services support plus addressing (e.g., yourname+keyword@example.com), which can be useful for filtering.
  • Regular Expressions: Detailed regular expressions can validate email syntax, but might reject valid addresses if too strict.
  • Email Confirmation: Sending a confirmation email is a reliable way to validate addresses, verifying both existence and user access.
  • Typo Detection: Real-time typo detection during email entry helps prevent common errors.
  • Valid Characters: Valid addresses can contain alphanumeric characters, periods, underscores, plus signs, and hyphens.
  • Disposable Addresses: Detecting and preventing disposable email addresses is important for list quality.
  • Email Format: A correctly formatted email address consists of a local-part, the @ symbol, and a domain.

Key considerations

  • Deliverability: Focus on deliverability checks, as overly strict syntax validation can reject valid addresses.
  • List Hygiene: Email validation is crucial for maintaining a clean list and protecting sender reputation.
  • Complexity: Email validation is not simple, as email syntax and deliverability has many different facets.
Marketer view

Email marketer from MailerCheck emphasizes the importance of detecting disposable email addresses during email validation. These temporary addresses can lead to deliverability issues and skewed marketing metrics.

January 2023 - MailerCheck
Marketer view

Email marketer from Kickbox emphasizes the importance of email validation to maintain a clean email list, improve deliverability, and protect sender reputation. They explain that validating emails helps prevent bounces, spam complaints, and blacklisting.

January 2025 - Kickbox
Marketer view

Email marketer from Email Hippo suggests implementing real-time typo detection as users type their email addresses. This helps prevent common errors like misspellings and missing dots, ensuring more accurate email capture.

July 2023 - Email Hippo
Marketer view

Email marketer from Super User points out that many email services support plus addressing (e.g., yourname+keyword@example.com), which can be useful for filtering and tracking. However, overly strict validation might reject these valid addresses.

August 2024 - Super User
Marketer view

Email marketer from Email Geeks shares a trick to create valid email addresses using '+something' with Gmail, routing all incoming mail to the base address. For example, <mailto:example+this@gmail.com|example+this@gmail.com> and <mailto:example+that@gmail.com|example+that@gmail.com> will both route to <mailto:example@gmail.com|example@gmail.com>.

June 2024 - Email Geeks
Marketer view

Email marketer from Medium explains that valid email addresses can contain a wide range of characters, including alphanumeric characters, periods, underscores, plus signs, and hyphens, in the local part before the @ symbol. The domain part should follow standard domain naming conventions.

July 2024 - Medium
Marketer view

Email marketer from Reddit recommends sending a confirmation email as the best way to validate an email address. This confirms the email exists and the user has access to it, rather than relying solely on syntax checks.

December 2021 - Reddit
Marketer view

Email marketer from example.com shares common valid email address examples such as <mailto:firstname.lastname@example.com|firstname.lastname@example.com>, <mailto:email@subdomain.example.com|email@subdomain.example.com>, <mailto:email@123.123.123.123|email@123.123.123.123>, and <mailto:email@[2001:db8::1]|email@[2001:db8::1]>, highlighting various allowed formats.

November 2021 - example.com
Marketer view

Email marketer from NeverBounce explains that a correctly formatted email address consists of a local-part, the @ symbol, and a domain. The local-part can contain alphanumeric characters and certain special characters, while the domain must be a valid domain name.

June 2021 - NeverBounce
Marketer view

Email marketer from Stack Overflow shares a detailed regular expression for validating email addresses, accounting for various valid formats, and explains the nuances of email address syntax according to RFC specifications.

July 2021 - Stack Overflow

What the experts say
4Expert opinions

Experts emphasize the complexity of email address syntax, noting the allowance of special and internationalized characters. Overly strict validation using regular expressions is discouraged. Instead, a focus on deliverability checks, such as sending test emails and monitoring bounces, is recommended to ensure an email address is valid and accepting mail. Modern email addresses can also have full unicode in the domain including internationalized TLDs.

Key opinions

  • Complex Syntax: Email address syntax is complex, allowing special and internationalized characters.
  • Unicode Support: Full unicode in the domain is supported including internationalized TLDs.
  • Deliverability Focus: Focus on deliverability checks rather than strict syntax validation.
  • Test Emails: Sending test emails and checking for bounces is a reliable validation method.

Key considerations

  • Regex Limitations: Avoid overly strict regular expressions as they may reject valid addresses.
  • Bounce Monitoring: Monitor bounces to verify if an address is accepting mail.
  • Modern Standards: Take into account internationalized domain names when validating email addresses.
Expert view

Expert from Word to the Wise (Laura Atkins) explains that modern email address syntax is incredibly complex, allowing for various special characters and even internationalized characters. She recommends against trying to validate addresses with overly strict regular expressions and suggests focusing on deliverability checks instead.

October 2022 - Word to the Wise
Expert view

Expert from Email Geeks explains that most of the provided email examples are syntactically valid, even if they are not deliverable. He also states you can have full unicode in the domain part of email addresses, including internationalized TLDs.

September 2022 - Email Geeks
Expert view

Expert from Email Geeks shares a link to an article that might be helpful for understanding email address structure: <https://wordtothewise.com/2009/03/what-is-an-email-address-part-three/>

June 2023 - Email Geeks
Expert view

Expert from Word to the Wise (Laura Atkins) suggests that the most reliable way to validate an email address is to send a test email and check for bounces. This verifies that the address exists and is accepting mail.

October 2021 - Word to the Wise

What the documentation says
4Technical articles

Documentation sources highlight various approaches to email address validation. IETF's RFC 5322 defines the formal syntax, detailing allowed characters and structure. MSDN provides an example using .NET regular expressions but acknowledges limitations, such as TLD validation. OWASP advises against overly strict regex validation due to complexity, recommending relaxed patterns or email confirmation. Verimail emphasizes comprehensive validation services that check beyond syntax, including domain, mailbox existence, and spam trap detection for deliverability.

Key findings

  • RFC 5322: Defines the formal syntax for email addresses.
  • Regex Validation: Regular expressions can be used, but have limitations.
  • OWASP Recommendation: Overly strict regular expressions should be avoided.
  • Comprehensive Validation: Email validation services offer checks beyond syntax.

Key considerations

  • Complexity: Email address syntax is complex, making strict validation difficult.
  • Validation Levels: Consider validation beyond syntax, including domain and mailbox existence.
  • Email Confirmation: Email confirmation is a reliable alternative or supplement to regex.
Technical article

Documentation from OWASP advises against strict email validation using regular expressions, highlighting the complexity of email address syntax and the risk of rejecting valid addresses. It suggests using a more relaxed pattern or relying on email confirmation.

August 2022 - OWASP
Technical article

Documentation from ietf.org defines the Internet Message Format, detailing the syntax for email addresses, including local-part and domain structure, allowed characters, and the use of quoted strings and comments.

June 2022 - ietf.org
Technical article

Documentation from Verimail explains that email validation services check email addresses at multiple levels, including syntax, domain existence, mailbox existence, and spam trap detection, to ensure high deliverability and data quality.

July 2022 - Verimail
Technical article

Documentation from MSDN explains how to validate an email address using regular expressions in .NET. The expression checks for a valid local part, @ symbol, and domain. It also discusses some limitations, such as not checking for valid TLDs.

August 2024 - MSDN