Summary
The validity and deliverability of email addresses with multiple or misplaced periods depend significantly on the email service provider. While established Internet Engineering Task Force (IETF) specifications, specifically RFC 3696 and RFC 5322, clearly prohibit periods at the start or end of the local part of an email address, or consecutive periods (e.g., name..surname@domain.com), Gmail exhibits a unique behavior. Gmail largely disregards single periods in the local part, treating variations like john.doe@gmail.com and johndoe@gmail.com as the same address, which makes addresses with multiple single periods deliverable to Gmail inboxes. However, even Gmail enforces the rule against two consecutive periods. In contrast, most other major email providers, including Outlook.com and Yahoo, treat periods as distinct characters and generally adhere more strictly to RFC standards. Consequently, email addresses violating these specifications, such as those with consecutive or leading-trailing periods, are widely considered invalid, are highly likely to result in hard bounces, and can negatively impact a sender's reputation if used in email campaigns.
Key findings
- RFCs Define Invalidity: According to Internet Engineering Task Force (IETF) specifications, particularly RFC 3696 and RFC 5322, email addresses are considered syntactically invalid if the local part begins or ends with a period, or if it contains consecutive periods (e.g., 'user..name@domain.com').
- Gmail Ignores Single Periods: Gmail has a unique policy where it ignores single periods in the local part of an email address, treating variations like 'john.doe@gmail.com' and 'johndoe@gmail.com' as the same inbox, meaning addresses with multiple single periods are deliverable to Gmail.
- Consecutive Periods Are Invalid: Across virtually all email providers, including Gmail, Yahoo, and Outlook.com, email addresses containing two or more consecutive periods are universally considered invalid and will result in delivery failure.
- Other Providers Are Strict: Most email service providers, excluding Gmail, treat periods as distinct characters and adhere more strictly to RFC validation rules, meaning addresses with misplaced or non-standard period placements will likely be flagged as invalid.
- Deliverability Risk is High: Sending emails to addresses that violate standard RFC syntax, especially those with consecutive periods or periods at the local part's start or end, will typically lead to hard bounces, which can severely damage sender reputation and overall deliverability.
- ESPs Validate Strictly: Many Email Service Providers (ESPs) employ rigorous validation processes that will automatically reject or skip records with syntax errors, even if a specific mail server might otherwise be lenient, emphasizing the importance of clean list hygiene.
Key considerations
- Adhere to RFC Standards: For the highest deliverability rates across all email providers, always ensure email addresses strictly conform to RFC standards, specifically by avoiding consecutive periods or periods at the beginning or end of the local part of the address.
- Understand Gmail's Unique Handling: Be aware that Gmail's behavior of ignoring single periods in the local part of an email address is unique to its domain and does not apply universally to other email service providers or mail servers.
- Prioritize List Hygiene: Regularly validate your email lists to identify and remove addresses that contain invalid period placements, as this proactive step helps prevent bounces and protects your sender reputation.
- Check ESP Validation Rules: Recognize that your Email Service Provider's (ESP) validation rules may be more stringent than some individual mail servers, potentially leading to bounces or skipped records for non-standard addresses even if they might otherwise be accepted elsewhere.
- Validate All Addresses: While some older or less compliant systems might occasionally accept non-standard formats, prioritize sending only to demonstrably valid email addresses to ensure successful delivery and maintain a healthy sending reputation.
What email marketers say
11 marketer opinions
Email addresses with multiple or misplaced periods are generally considered invalid for deliverability, with significant implications for sender reputation. While Internet Engineering Task Force (IETF) specifications, such as RFC 3696, clearly define that periods should not appear consecutively or at the beginning or end of the local part of an email address, real-world application varies. Gmail stands out as an exception, uniquely ignoring single periods in the local part (e.g., treating 'john.doe@gmail.com' and 'johndoe@gmail.com' as the same address). However, even Gmail enforces the rule against two consecutive periods. Most other major email providers and validation services strictly adhere to the RFC standards. This means that sending to addresses with consecutive periods or those starting/ending with a period in the local part will almost certainly lead to hard bounces, damaging a sender's reputation and overall email deliverability.
Key opinions
- Syntactic Invalidity by RFCs: Email addresses containing consecutive periods (e.g., 'name..surname@domain.com') or periods at the start or end of the local part are widely considered syntactically incorrect according to standard email protocols (RFCs).
- Gmail's Unique Handling (Limited): While Gmail uniquely ignores single periods in the local part of an email address, this behavior does not extend to consecutive periods, and this specific leniency is unique to Gmail, not a universal standard.
- High Bounce Rate & Reputation Risk: Sending to such invalid email addresses typically results in hard bounces, which severely damages sender reputation, leading to lower deliverability and potential blacklisting by mail servers.
- ESP Strictness: Most Email Service Providers (ESPs) and email validation services will flag addresses with misplaced or multiple periods as undeliverable or syntax errors, often skipping these records even if they were previously opted in.
- Universal Invalidity for Consecutive Periods: Email addresses with consecutive periods are almost universally considered invalid by mail servers and will typically result in a bounce, indicating an invalid recipient across various providers.
Key considerations
- Adhere to RFC Standards: For optimal deliverability across all platforms, consistently ensure that email addresses adhere strictly to RFC standards, specifically by avoiding consecutive periods or periods at the beginning or end of the local part.
- Do Not Rely on Gmail's Exception: Marketers should recognize that Gmail's unique handling of single periods is an exception and does not apply to other email service providers or general mail servers. This behavior should not be relied upon for universal deliverability.
- Proactive List Validation: Implement rigorous email list validation processes to identify and remove addresses containing invalid period placements before sending. This proactive measure significantly reduces bounce rates and protects your sender reputation.
- Understand ESP Validation: Be aware that your chosen Email Service Provider's (ESP) internal validation rules may be more stringent than some individual mail servers, potentially leading to records being skipped or rejected even if they were otherwise opted in.
- Minimize Deliverability Risk: Prioritize sending only to demonstrably valid email addresses. Sending to malformed addresses, including those with misplaced or multiple periods, will almost certainly result in bounces, damaging your sender reputation and overall deliverability.
Marketer view
Marketer from Email Geeks states that two consecutive dots are not valid in email addresses, referencing RFC 3696 which specifies that a dot may not appear consecutively unless quoted, or be the first or last character unless quoted.
7 Jun 2023 - Email Geeks
Marketer view
Marketer from Email Geeks explains that the local part of an email address cannot start or end with a dot, or have consecutive dots, unless it is quoted, according to the specification. He clarifies that treating an email address with dots as the same as one with the dots removed is a behavior unique to Gmail and Gapps.
19 Nov 2023 - Email Geeks
What the experts say
4 expert opinions
The deliverability of email addresses containing multiple or misplaced periods hinges significantly on the email service provider. Gmail stands out by uniquely disregarding single periods within the local part of an email address, treating 'first.last@gmail.com' and 'firstlast@gmail.com' as identical and deliverable to the same inbox. This specific behavior means that addresses with multiple single periods are valid and deliverable to Gmail accounts, assuming the base address is otherwise correct. However, this flexibility does not extend to consecutive periods; addresses with two or more dots in a row (e.g., 'user..name@domain.com') are universally considered invalid by all major email services, including Gmail and Yahoo, and will consistently result in delivery failures. For email domains other than Gmail, period placement is generally critical, and addresses must strictly adhere to the specific server's expected format for successful delivery.
Key opinions
- Gmail Dot Leniency: Gmail's system ignores single periods within the local part of an email address, treating 'john.doe@gmail.com' and 'johndoe@gmail.com' as functionally identical and deliverable to the same inbox.
- Universal Consecutive Dot Invalidity: Email addresses containing two or more consecutive periods are universally invalid and non-deliverable across all major email service providers, including Gmail and Yahoo.
- Domain-Specific Period Rules: The validity of period placement is domain-specific; while Gmail is lenient, most other mail servers strictly interpret period placement, requiring addresses to conform to their specific format for deliverability.
- Do Not Remove Valid Gmail Variations: Email addresses should not be removed from mailing lists solely because they contain single periods, especially if they are Gmail accounts, as these variations are often legitimate and deliverable.
- Practical Validation Confirms Invalidity: Real-world tests confirm that attempts to send emails to addresses with consecutive periods are consistently rejected by services like Gmail and Yahoo.
Key considerations
- Understand Gmail's Unique Handling: Be aware that Gmail's policy of ignoring single periods in the local part is an exception and does not apply to other email service providers, requiring different validation considerations for non-Gmail addresses.
- Prioritize Removing Consecutive Periods: Always validate and remove email addresses that contain two or more consecutive periods, as these are universally invalid and will lead to hard bounces, harming sender reputation.
- Respect Domain-Specific Syntax: For non-Gmail domains, ensure that email addresses adhere to standard syntax rules where period placement matters, as these servers will not ignore dots as Gmail does.
- Avoid Over-Filtering Based on Dots: Do not overly aggressively filter out email addresses simply for containing single periods, especially for Gmail addresses, as many of these are valid and belong to active subscribers.
- Maintain Robust List Hygiene: Implement a comprehensive list hygiene strategy that accounts for both Gmail's leniency and the universal invalidity of consecutive periods to optimize deliverability and minimize bounce rates.
Expert view
Expert from Email Geeks explains that single dots are ignored by Gmail and are valid. However, Gmail does enforce that two consecutive dots are not valid. She advises not to remove email addresses simply for having dots, unless there are two or more in a row, as many companies use dots as separators in usernames.
29 Oct 2024 - Email Geeks
Expert view
Expert from Email Geeks shares practical test results, demonstrating that both Gmail and Yahoo email services would not allow sending emails to addresses containing two consecutive dots, confirming their invalidity.
18 Sep 2023 - Email Geeks
What the documentation says
5 technical articles
The deliverability of email addresses with multiple or misplaced periods is highly dependent on the recipient's email service, even though clear Internet Engineering Task Force, IETF, standards exist. IETF RFCs, such as 5322 and 3696, specify that periods should not begin or end the local part of an address, nor should they appear consecutively, for example, 'user..name@domain.com'. Most legitimate mail servers, including those for Outlook.com, strictly enforce these RFC rules, rejecting non-compliant addresses outright. Gmail, however, presents a significant exception: it uniquely disregards single periods within the local part of an address, treating variations like 'john.doe@gmail.com' and 'johndoe@gmail.com' as functionally identical and deliverable to the same inbox. This specific behavior means that single-period variations are deliverable to Gmail accounts. Nevertheless, even Gmail upholds the universal rule against consecutive periods; such addresses are always considered invalid and will consistently lead to delivery failure. Using email addresses that violate these general rules, particularly those with consecutive periods, will result in hard bounces and can severely harm sender reputation.
Key findings
- RFC Syntax Requirements: Internet Engineering Task Force (IETF) RFCs establish that email addresses are syntactically invalid if the local part contains consecutive periods or starts or ends with a period.
- Gmail's Period Leniency: Gmail uniquely ignores single periods within the local part of an email address, treating variations such as 'john.doe@gmail.com' and 'johndoe@gmail.com' as the same inbox, a behavior specific to Gmail addresses.
- Universal Consecutive Dot Rejection: All major email providers, including Gmail, universally reject email addresses containing two or more consecutive periods, leading to guaranteed delivery failure.
- Provider-Specific Dot Interpretation: Most email service providers, like Outlook.com, treat periods as distinct characters and adhere strictly to RFC rules regarding their placement, unlike Gmail's unique handling.
- Deliverability Risk from Invalid Dots: Sending emails to addresses with invalid period placements, especially consecutive periods, results in hard bounces, severely damaging sender reputation and overall deliverability.
Key considerations
- Adhere to RFC Standards: For optimal deliverability across all platforms, consistently ensure that email addresses strictly conform to RFC standards by avoiding consecutive periods or periods at the beginning or end of the local part.
- Do Not Rely on Gmail's Exception: Understand that Gmail's unique handling of single periods in the local part is an exception and does not apply to other email service providers; universal leniency cannot be assumed.
- Validate for Consecutive Periods: Implement robust email list validation to identify and remove all email addresses that contain two or more consecutive periods, as these are universally invalid and will lead to hard bounces.
- Respect Domain-Specific Rules: Be aware that for most non-Gmail domains, period placement within the local part is critical, and addresses must strictly adhere to the specific server's expected format for successful delivery.
- Maintain Proactive List Hygiene: Regularly cleanse your email lists to eliminate addresses with syntactical errors related to period placement, which reduces bounce rates, preserves sender reputation, and improves campaign performance.
Technical article
Documentation from Internet Engineering Task Force (IETF) - RFC 5322 explains that the local-part of an email address (the part before the '@') must not start or end with a period character '.', and the period character must not appear consecutively (e.g., 'a..b@example.com' is invalid).
23 Oct 2021 - Internet Engineering Task Force (IETF) - RFC 5322
Technical article
Documentation from Internet Engineering Task Force (IETF) - RFC 3696 clarifies that the local-part of an email address cannot have two consecutive periods, nor can it start or end with a period. It emphasizes that while some systems might accept addresses that violate these rules, they are technically non-compliant.
13 Oct 2021 - Internet Engineering Task Force (IETF) - RFC 3696
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