Summary
RFC 2047 encoding is a technique for representing non-ASCII characters within specific sections of email headers. The consensus across experts, marketers, and documentation is that RFC 2047 encoding should primarily be used for the display name (also known as the friendly name or phrase) associated with an email address in the From, To, and Cc headers, as well as in the Subject and Comments headers. The actual email address (the 'addr-spec') must remain in standard US-ASCII format. Encoding the email address itself is discouraged and can be seen as a security risk. Furthermore, it is invalid to use RFC 2047 encoding in List-Unsubscribe headers.
Key findings
- Display Name Focus: RFC 2047 is primarily intended for encoding the display name (or friendly name) in email headers.
- Address Restriction: The actual email address (addr-spec) must remain in US-ASCII format.
- Security Concerns: Encoding the entire email address poses a security risk and may allow malicious addresses to be hidden.
- Valid Header Sections: RFC 2047 encoding is valid in the Subject, Comments, and the display name portions of From, To, and Cc headers.
- Invalid Header Sections: RFC 2047 encoding is invalid in List-Unsubscribe headers.
Key considerations
- Character Encoding: When using special or international characters, ensure only the display name is encoded, not the email address itself.
- Header Compliance: Follow RFC 2047 specifications when encoding header fields to ensure proper rendering across various email clients.
- Security Awareness: Be mindful of the security implications of encoding and avoid practices that could mask malicious addresses.
- List-Unsubscribe Avoidance: Do not use RFC 2047 encoding in List-Unsubscribe headers as it is not valid and may cause issues.
- Documentation Reference: Refer to RFC 2047 Section 5 for details on what can be replaced by an encoded word in email headers.
What email marketers say
10 marketer opinions
RFC 2047 encoding is used to represent non-ASCII characters in email headers, specifically within the display name (or friendly name) portion of email addresses (e.g., in the From, To, and Cc fields). The actual email address itself must remain in standard US-ASCII format. Encoding the email address is often seen as a security risk because it can be used to hide malicious addresses.
Key opinions
- Display Name Encoding: RFC 2047 is primarily for encoding the display name or friendly name associated with an email address.
- Address Restriction: The actual email address (the part before and after the @ symbol) must remain in US-ASCII.
- Security Risk: Encoding the entire email address can create a security vulnerability by allowing malicious actors to disguise harmful addresses.
Key considerations
- Special Characters: When using special or international characters, ensure you are only encoding the display name and not the email address itself.
- Header Encoding: Use RFC 2047 methods to properly encode the header fields, especially the display name, to ensure they are displayed correctly across different email clients.
- Security Implications: Be aware of the security implications of encoding email addresses and avoid any practice that could be used to mask malicious addresses.
Marketer view
Email marketer from Email Marketing Forum responds that if you want to encode a name with special characters in the from field, use RFC 2047 encoding for the name portion, leaving the email address itself in ASCII.
21 Apr 2024 - Email Marketing Forum
Marketer view
Email marketer from Campaign Monitor shares that encode the header fields, particularly the display name, according to RFC 2047 to ensure international characters display correctly in different email clients. However, the actual email address component should remain in standard ASCII.
8 Jun 2025 - Campaign Monitor
What the experts say
3 expert opinions
RFC 2047 encoding is restricted to specific parts of email headers. It is valid for human-readable text, such as the Subject line, comments, and the display name portion of From, To, and Cc headers. Encoding the actual email address itself is invalid. Additionally, RFC 2047 encoding is not allowed in List-Unsubscribe headers.
Key opinions
- Limited Encoding Scope: RFC 2047 encoding is limited to specific areas within email headers.
- Valid Uses: Valid uses include the Subject line, comments, and display names in From, To, and Cc headers.
- Invalid Uses: Encoding the email address itself and using RFC 2047 in List-Unsubscribe headers are not permitted.
Key considerations
- Header Sections: Pay close attention to which sections of the email header you're encoding to ensure compliance with RFC 2047.
- Human Readability: Only encode human-readable parts; machine-readable parts like the email address should remain in their original format.
- List-Unsubscribe Restrictions: Avoid using RFC 2047 encoding within List-Unsubscribe headers, as this is considered invalid.
Expert view
Expert from Word to the Wise mentions that RFC 2047 encoding in List-Unsubscribe headers is invalid. RFC 2047 encoding is allowed in the display name part of the From, To, and CC headers, and in the Subject and Comments headers.
2 Aug 2024 - Word to the Wise
Expert view
Expert from Email Geeks shares RFC 2047 #5, specifying what may be replaced by an encoded word, which is a short list of places you’re allowed to do that - Subject, Comments headers, any parenthesised comment or the phrase preceding an address in From, To, Cc.
15 May 2024 - Email Geeks
What the documentation says
4 technical articles
RFC 2047 defines how to represent non-US-ASCII characters in email header fields. This encoding is applied to specific parts of the message header, including 'Subject', 'Comments', and the display name (or phrase portion) within address fields like 'From', 'To', and 'Cc'. The actual email address ('addr-spec') itself must remain in US-ASCII characters. RFC 5322 reinforces that the email address must conform to ASCII syntax, while allowing the display name to be encoded.
Key findings
- Encoding Purpose: RFC 2047 is used to represent non-ASCII characters in email headers.
- Header Field Scope: It applies to specific header fields such as 'Subject', 'Comments', and the display name within address fields.
- Address Limitation: The actual email address ('addr-spec') must remain in US-ASCII.
Key considerations
- Character Set Support: Use RFC 2047 when needing to display international characters in email headers.
- Field Selection: Ensure you are only applying the encoding to the appropriate header fields and portions within those fields (e.g., the display name).
- Address Compliance: Always keep the actual email address in standard ASCII format.
Technical article
Documentation from Microsoft explains that to display international characters in email headers, you must use MIME encoding (RFC 2047). This encoding is applied to header fields like Subject, From, To, etc. but is primarily intended for the descriptive text, not the email address itself.
30 Jun 2021 - Microsoft Documentation
Technical article
Documentation from Word to the Wise explains that RFC 2047 allows encoding of the text part of headers such as Subject, Comments, and certain parts of address fields (From, To, CC), such as the display name, but not the email address itself. It refers to Section 5 of RFC 2047.
20 Jan 2024 - Word to the Wise
