Summary
Gmail's 'sender's email address uses abnormal characters' error is a multifaceted issue primarily rooted in character-related problems. The presence of characters outside the standard ASCII set, including accented letters, Cyrillic characters, and other special symbols, triggers the error. These invalid characters may be introduced through copy-pasting, where hidden characters are added, or arise from character encoding mismatches, particularly when not using UTF-8. While certain special characters are technically permissible under RFC specifications, not all email providers support them, leading to compatibility issues. Furthermore, older email systems' limitations in handling non-ASCII characters can contribute to the error. While less common, underlying deliverability problems and sender reputation may also trigger this message. Solutions involve careful validation of email addresses, ensuring correct character encoding, avoiding copy-pasting, and considering the capabilities of older systems.
Key findings
- Invalid Character Sets: Presence of non-ASCII characters, accented letters, Cyrillic characters, or special symbols in the sender's email address.
- Encoding Incompatibilities: Mismatched or incorrect character encoding, often due to the absence of UTF-8 encoding.
- Hidden Characters: Introduction of hidden or unsupported characters through copy-pasting.
- System Limitations: Inability of older email systems to support internationalized characters.
- Deliverability Factors: Potential link to underlying deliverability issues or a poor sender reputation, though less common.
- RFC Compliance Issues: Deviation from the defined syntax in RFC specifications concerning allowed characters.
Key considerations
- Address Validation: Implement robust validation checks to ensure email addresses contain only supported characters.
- Encoding Standardization: Maintain consistency with UTF-8 encoding throughout the email sending process.
- Avoid Copy-Pasting: Advocate manual entry of email addresses to mitigate the risk of including hidden characters.
- Legacy System Compatibility: Account for potential incompatibilities with older email systems by limiting the use of non-ASCII characters.
- Reputation Management: Address any deliverability problems and monitor sender reputation to prevent related errors.
- Syntax Adherence: Ensure full compliance with RFC email address syntax guidelines.
What email marketers say
9 marketer opinions
Gmail's 'sender's email address uses abnormal characters' error is primarily caused by the presence of characters outside the standard ASCII set in the sender's email address. This can include accented letters, Cyrillic characters, or other special symbols, as well as seemingly standard characters that are actually visually similar but encoded differently. The issue can stem from character encoding problems (especially non-UTF-8), copy-pasting errors introducing hidden characters, or limitations in older email systems. Though less common, deliverability problems and sender reputation can also contribute.
Key opinions
- Invalid Characters: The most common cause is the presence of invalid or unsupported characters in the 'From' address, often stemming from non-ASCII characters.
- Encoding Issues: Incorrect character encoding (e.g., not using UTF-8) can lead to misinterpretation of characters.
- Hidden Characters: Copy-pasting email addresses can introduce hidden or unusual characters that are not immediately visible.
- Legacy System Incompatibility: Older email systems may not fully support internationalized characters or newer encoding standards.
- Deliverability Impact: While less common, underlying deliverability issues or a poor sender reputation can sometimes trigger this error message.
Key considerations
- Character Validation: Thoroughly validate email addresses to ensure they only contain allowed characters and adhere to standard formatting.
- Encoding Standards: Ensure consistent use of UTF-8 encoding throughout the email sending process.
- Manual Entry: When possible, manually type email addresses to avoid introducing hidden characters from copy-pasting.
- System Compatibility: Consider the capabilities of older email systems when sending to a diverse audience.
- Monitor Reputation: Proactively monitor sender reputation and address any deliverability problems to prevent related errors.
Marketer view
Marketer from Email Geeks warns about Cyrillic 'a', and potential issues with 'I' and 'l' characters.
15 Sep 2024 - Email Geeks
Marketer view
Email marketer from Stack Overflow explains that certain special characters, while technically allowed in the local part of an email address according to RFC specifications, may not be supported by all email providers. Using these characters can lead to compatibility issues.
3 Oct 2024 - Stack Overflow
What the experts say
2 expert opinions
The 'abnormal characters' error in Gmail sender email addresses often arises from character encoding problems, where systems misinterpret or lack support for specific character sets, leading to the error. Cleaning and validating email addresses to ensure they contain only supported characters is crucial.
Key opinions
- Character Encoding: Character encoding issues are a frequent cause of 'abnormal characters' errors.
- Data Validation: Invalid or unsupported characters in email addresses contribute to the problem.
Key considerations
- Encoding Compatibility: Ensure character sets are compatible across systems during transmission and storage.
- Address Validation: Clean and validate email addresses to only include supported characters for improved deliverability.
Expert view
Expert from Spam Resource (Laura Atkins) explains that character encoding issues are a frequent cause. Some systems may misinterpret or fail to support specific character sets, leading to the 'abnormal characters' error. Encoding mismatches during the transmission or storage of the email address can result in the same problem.
22 Jun 2021 - Spam Resource
Expert view
Expert from Word to the Wise discusses the importance of cleaning up data in email addresses to ensure they are valid. It explains that if someone is getting the 'abnormal characters' error, it is likely due to the fact that email addresses that contain characters that aren't supported.
29 May 2025 - Word to the Wise
What the documentation says
3 technical articles
The 'abnormal characters' error in Gmail sender email addresses arises from deviations from established email address syntax and limitations in character support. RFC specifications define the allowed characters, while platforms like Exchange Online enforce specific limits. Internationalized email addresses (containing non-ASCII characters) are addressed in IETF standards, but inconsistent support can lead to errors.
Key findings
- RFC Compliance: Email addresses must adhere to the syntax specified in RFC standards.
- Platform Limits: Platforms like Exchange Online impose specific limits on email address length and allowed characters.
- Internationalization Issues: Inconsistent support for internationalized email addresses (non-ASCII characters) can trigger errors.
Key considerations
- Syntax Validation: Ensure email addresses conform to RFC-defined syntax and character sets.
- Platform Restrictions: Adhere to specific limitations and requirements imposed by the email platform being used (e.g., Exchange Online).
- International Address Support: Carefully consider the support for internationalized email addresses when sending emails, accounting for potential inconsistencies.
Technical article
Documentation from IETF addresses the use of internationalized email addresses (addresses containing non-ASCII characters). While the standards exist, support can be inconsistent, and systems might not handle these addresses correctly, leading to errors.
23 Aug 2021 - IETF
Technical article
Documentation from RFC Editor specifies the syntax for email addresses, including the allowed characters in the local part (before the '@' symbol) and the domain part. It clarifies which characters require quoting and which are explicitly disallowed.
15 Feb 2024 - RFC Editor
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