Are email addresses with multiple or misplaced periods valid for deliverability?

Key findings

• Gmail's unique handling: Gmail ignores periods in the local part of an email address, meaning john.doe@gmail.com and johndoe@gmail.com are treated as the same address. However, this normalization does not extend to consecutive periods or periods at the start or end of the local part.
• RFC standards: RFC 3696 (and other related RFCs) state that dots cannot be the first or last character of the local part, nor can they appear consecutively, unless the entire local part is enclosed in quotes. Most systems do not support quoted local parts for regular mail flow.
• ESP validation: Many Email Service Providers (ESPs) perform their own syntax validation. Addresses with consecutive periods or misplaced periods (e.g., before the @ symbol) are often flagged as invalid by ESPs, even if some mailbox providers might interpret them differently, leading to skipped deliveries.
• Non-Gmail behavior: Mailbox providers like Yahoo, AOL, and educational institutions (.edu domains) do not typically normalize periods in the same way Gmail does. They generally adhere more strictly to RFC standards regarding dot placement, making malformed addresses undeliverable.
• Impact on deliverability: Addresses that violate RFC standards for dot placement are generally undeliverable. If an ESP or mail server rejects such addresses due to syntax errors, the email will not reach the recipient, negatively impacting deliverability rates.

Key considerations

• List hygiene: Regularly cleaning your email list to remove addresses with invalid period formatting is crucial. Focusing on removing addresses with consecutive periods or those placed at the start/end of the local part will significantly improve list quality.
• Validation tools: Utilize email validation services to identify and correct (if appropriate and legally permissible) or remove addresses with problematic period placements. This prevents hard bounces and protects your sender reputation.
• Avoid assumptions: Do not assume that all email providers handle periods like Gmail does. Treating all non-standard period placements as potentially invalid is a safer approach for broad deliverability.
• Consent and data integrity: Be cautious about programmatically altering email addresses to make them valid. If an address was fat-fingered during sign-up, altering it could lead to sending to unintended recipients, raising privacy and legal concerns. It is often safer to confirm or remove such addresses.
• Monitoring bounces: Pay close attention to bounce reports from your ESP. Consistent hard bounces due to syntax errors indicate a need for list cleanup. Regularly checking your deliverability metrics is key.

Key opinions

• Common formatting errors: Marketers frequently identify addresses with multiple consecutive periods or periods before the @ symbol as 'fat-fingered' mistakes from user input.
• ESP-level rejection: Many ESPs are reported to have strict syntax validation, causing them to skip sending to addresses with non-standard period placements, even if the address might technically be valid for certain mailbox providers like Gmail.
• Gmail's period normalization: It's a common understanding among marketers that Gmail treats addresses with or without periods in the local part as identical for delivery purposes, though this is unique to Gmail.
• List clean-up priority: Prioritizing the clean-up of obvious syntax errors (like consecutive dots) is a practical approach for improving deliverability and maintaining list health.
• User intent: Some users intentionally use dots in their Gmail addresses for organizational purposes (e.g., filtering), which can lead to confusion if marketers assume all dots are errors.

Key considerations

• Proactive list hygiene: Implement robust email validation at the point of data capture to minimize the entry of malformed addresses. This reduces the need for extensive post-acquisition cleaning.
• ESP compatibility: Understand how your specific ESP handles email address validation. If it rejects addresses with certain period placements, those addresses should be marked as undeliverable or removed from your active sending list.
• Impact on deliverability rates: Even if an address is theoretically valid for a specific provider, if your ESP rejects it, it will contribute to a lower deliverability rate. Focusing on general deliverability best practices across all recipients is key.
• Ethical considerations: Avoid making assumptions about user intent based on dot placement. Respect user subscriptions and consider re-engagement campaigns or confirmation emails for addresses with questionable formatting rather than unilateral removal or alteration. More on email deliverability best practices.

Key opinions

• Gmail's dot policy: Experts confirm that Gmail internally normalizes periods in the local part, treating first.last@gmail.com as firstlast@gmail.com. However, this rule does not apply to consecutive dots or dots at the start/end of the local part.
• RFC compliance: The RFC standards explicitly prohibit consecutive dots and leading/trailing dots in the unquoted local part of an email address. Adhering to these is crucial for universal deliverability.
• Validation enforcement: While some older systems might be lenient, most modern email providers and ESPs will reject addresses that violate basic RFC syntax rules for periods.
• Risks of invalid addresses: Sending to malformed addresses leads to hard bounces, which can damage sender reputation and potentially result in IP or domain blocklisting (blacklisting).
• Legitimate dot usage: Many companies and individuals legitimately use single dots as separators in email usernames (e.g., john.smith@company.com), and these should not be considered invalid.

Key considerations

• Strict validation: Implement or use email validation services that strictly enforce RFC standards for email address syntax to catch and remove invalid entries from your list.
• Distinguish valid from invalid: Differentiate between legitimately formatted addresses with single dots and those with consecutive or misplaced dots, as only the latter are universally problematic. See our guide on how Gmail handles periods.
• Sender reputation: Sending to invalid addresses, including those with syntax errors, signals poor list management to mailbox providers. This can lead to decreased sender reputation and potentially landing on a spam blocklist.
• Continuous monitoring: Regularly monitor bounce codes to identify systematic issues related to email address formatting. This informs ongoing list cleaning and validation efforts, as outlined in expert deliverability guides.

Key findings

• RFC 3696 dot rules: RFC 3696 explicitly states that an unquoted local part of an email address must not begin or end with a dot, nor contain consecutive dots. These are common sources of syntax errors.
• Quoted local parts: The RFC allows for local parts to contain special characters, including consecutive dots, if the entire local part is enclosed in quotation marks. However, this format is rarely supported by mail systems for practical purposes.
• Gmail's period normalization: Google's official documentation confirms that periods in Gmail usernames are ignored, treating user.name@gmail.com and username@gmail.com as the same address.
• RFC 5322 context: RFC 5322, which defines the syntax for email messages, provides the overarching framework for email address structure, including the 'local-part' and 'domain' components.
• Mailbox provider expectations: Most mailbox providers expect incoming email addresses to adhere to established RFC standards for successful routing and delivery, flagging non-compliant addresses as errors.

Key considerations

• Adherence to universal standards: While specific providers may have unique internal rules (like Gmail's period handling), relying on these is risky for broad deliverability. Adhere to the more restrictive RFC standards for general email validity.
• System compatibility: Ensure your systems (ESPs, marketing automation platforms) validate email addresses in line with RFCs to prevent sending to addresses that will hard bounce due to syntax errors. Consider implementing robust email validation.
• Interpretation by MTAs: Mail Transfer Agents (MTAs) are programmed to interpret email addresses based on RFCs. Addresses with non-compliant period placements are likely to be rejected at the MTA level, regardless of the ultimate mailbox provider's internal policies.
• Source of truth: For definitive answers on email address validity, consult the latest IETF RFCs and specific documentation from major mailbox providers relevant to your recipient list.