Summary
Experts, marketers, and documentation sources overwhelmingly advise against using SMTP commands for email address validation. They cite the method's unreliability, inaccuracy, potential harm to sender and IP reputation, and the existence of superior dedicated validation services and APIs. SMTP validation is seen as an antiquated practice that offers limited guarantees about mailbox validity and can lead to false positives.
Key findings
- Unreliable and Inaccurate: SMTP validation doesn't reliably confirm email address validity and can produce misleading results due to server configurations.
- Negative Impact on Reputation: Using SMTP commands for validation can harm sender reputation, IP reputation, and overall deliverability.
- Outdated Method: SMTP validation is considered an antiquated practice, as modern email systems use more sophisticated techniques for abuse prevention.
- Limited Guarantee of Validity: SMTP commands only confirm that a server accepts mail for an address but not the mailbox's existence or active use.
Key considerations
- Use Dedicated Validation Services: Implement dedicated email validation services for increased accuracy and reliability.
- Explore Modern Validation APIs: Consider using comprehensive email verification APIs for more reliable results.
- Prioritize Sender Reputation: Focus on maintaining a positive sender reputation by avoiding methods that can negatively impact it.
- Evaluate Alternative Validation Techniques: Explore alternative email validation techniques that provide more accurate and reliable results than SMTP commands.
What email marketers say
7 marketer opinions
Email marketers generally advise against using SMTP commands for email validation. This method is considered unreliable and outdated, as modern email systems employ more advanced techniques for abuse prevention. SMTP validation can lead to inaccurate results due to server configurations that initially accept emails but later reject them. Using SMTP validation can negatively impact sender reputation, potentially causing harm to IP reputation and deliverability.
Key opinions
- Unreliable Validation: SMTP validation doesn't guarantee email address validity or activity, as servers may initially accept all addresses.
- Outdated Method: Modern email systems use sophisticated abuse prevention techniques, making SMTP validation ineffective.
- Reputation Damage: Using SMTP validation can harm sender and IP reputation, affecting deliverability.
- Inaccurate Results: Server configurations accepting emails initially but rejecting them later can lead to false positives with SMTP validation.
Key considerations
- Use Dedicated Services: Consider using dedicated email validation services for better accuracy and reliability.
- Validation Alternatives: Explore modern email validation techniques that provide more accurate results.
- Sender Reputation: Prioritize sender reputation by avoiding methods that can negatively impact it.
- Test Emails: Sending test emails and tracking engagement can provide a more reliable assessment.
Marketer view
Email marketer from EmailHippo explains that while SMTP validation may seem like a quick solution, it's often unreliable and can damage sender reputation. They recommend using a dedicated email validation service for better accuracy.
23 Feb 2022 - EmailHippo
Marketer view
Email marketer from Stack Overflow responds that using SMTP commands to validate emails is unreliable. The user shares that the process might seem valid but could be misleading due to server configurations that accept emails and reject them later.
13 Jun 2025 - Stack Overflow
What the experts say
3 expert opinions
Experts in email deliverability from Email Geeks, SpamResource, and Word to the Wise strongly discourage using SMTP commands for email address validation. They highlight that it's an antiquated, unreliable method that can negatively impact deliverability and damage sender reputation. Alternative, more robust validation methods or dedicated validation services are recommended instead.
Key opinions
- Negative Impact on Deliverability: Using SMTP VRFY and similar commands for validation can harm email deliverability.
- Antiquated and Unreliable: SMTP verification is an outdated method that doesn't accurately determine if an email address is valid or in use.
- Reputation Damage: Attempting to verify addresses using SMTP can damage your sender reputation.
Key considerations
- Explore Alternatives: Consider alternative, more reliable email validation methods.
- Dedicated Validation Services: If email validation is necessary, use dedicated validation services.
- Prioritize Reputation: Avoid SMTP validation to protect your sender reputation.
Expert view
Expert from SpamResource explains that using SMTP VRFY or similar commands for email validation can negatively impact deliverability. The article details different email verification methods and their impact on email deliverability.
6 Sep 2023 - SpamResource
Expert view
Expert from Word to the Wise answers the question of address verification. It highlights that using SMTP to verify addresses is an antiquated method. While you might determine if an email server exists, you cannot accurately determine if the email address is valid or in use. The article advises against attempting to verify addresses and damaging your reputation in the process.
30 Jan 2023 - Word to the Wise
What the documentation says
3 technical articles
Email documentation from RFC Editor, SendGrid, and Mailgun discourages using SMTP commands for email validation. While technically possible, it's not the intended purpose, can be unreliable, and may negatively impact sender reputation. They recommend using dedicated email validation services or APIs for more accurate results.
Key findings
- Not Intended Purpose: SMTP commands are designed for email transmission, not email address validation.
- Unreliable Validation: SMTP 'pinging' for email validation can be inaccurate and provide false positives.
- Reputation Impact: Using SMTP for validation can negatively affect sender reputation.
- Limited Guarantee: SMTP commands only confirm server acceptance, not mailbox existence or validity.
Key considerations
- Dedicated Services: Utilize dedicated email validation services for higher accuracy.
- Email Verification API: Consider using comprehensive email verification APIs for reliable results.
- Avoid Sole Reliance: Do not rely solely on SMTP for email address validation.
Technical article
Documentation from Mailgun advises against relying solely on SMTP for email validation. They explain that while SMTP commands can confirm if a server accepts mail for an address, they don't guarantee the mailbox's existence or validity. They recommend using a comprehensive email verification API.
31 Aug 2022 - Mailgun
Technical article
Documentation from RFC Editor explains that while SMTP commands could technically be used for verifying email addresses, it's not their intended purpose and can be unreliable. The proper use is for email transmission, not address validation.
21 Mar 2025 - RFC Editor
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