What causes 'Line Too Long' Docomo.ne.jp bounces and how to fix?
Summary
What email marketers say7Marketer opinions
Email marketer from Email Server Forum recommends checking and adjusting the mail transfer agent (MTA) settings to ensure that line length enforcement is properly configured or disabled if necessary, but with caution to avoid breaking email design.
Email marketer from Mailjet suggests examining the email's headers for unusually long lines, particularly within fields like 'Subject' or 'Received.' Encoding issues here can sometimes lead to this error.
Email marketer from Stack Overflow explains that the maximum line length in email headers is 998 characters, but recommends keeping it under 78 characters. Suggests using `mb_encode_mimeheader()` for PHP to encode headers correctly and split lines to prevent the issue.
Email marketer from Campaign Monitor recommends avoiding inline styles where possible and using CSS. Overly long inline styles can contribute to the 'Line Too Long' error.
Email marketer from EmailOnAcid suggests to keep your code clean and within limits by avoiding long lines that exceed the maximum character limit. They advise to review and refactor HTML code to ensure it adheres to email coding best practices, including line length constraints.
Email marketer from Reddit user suggests ensuring that the email uses the correct character encoding (UTF-8) and that long lines are properly encoded using quoted-printable or base64 encoding if necessary.
Email marketer from Litmus advises on using proper HTML structure to avoid generating extremely long lines of code. Proper nesting of HTML tags and using CSS for styling can help.
What the experts say4Expert opinions
Expert from Email Geeks recalls that the error means the email isn't properly encoding a CR/LF at the required number of characters (998).
Expert from Email Geeks explains that if non-ascii characters are used, you almost certainly need to be using quoted-printable or base64 content encoding. Also you should send a copy of that mail to somewhere you can see it, so you can see what was sent and how it's encoded then diagnose from there.
Expert from Word to the Wise explains that the issue is not always the sender’s fault, but more often a receiving system being very strict on line length enforcement. They also explain that some shops turn off line length enforcement because someone complains that their email design was broken by the forced linebreaks.
Expert from Spamresource.com explains that long lines in email headers or body (exceeding RFC 5322 limits) can trigger 'Line Too Long' errors. It is important to ensure proper character encoding (like UTF-8) and using quoted-printable or base64 encoding for non-ASCII characters.
What the documentation says3Technical articles
Documentation from RFC Editor details the Internet Message Format. It specifies that each line of characters MUST be no more than 998 characters, and SHOULD, be no more than 78 characters, excluding the CRLF. This ensures compatibility across different email systems.
Documentation from Microsoft explains that 'Line Too Long' error appears due to exceeded character limits in the message body or headers. Encoding issues and improper handling of attachments can cause this. It recommends breaking long lines and ensuring correct MIME encoding.
Documentation from SmarterTools explains that the SMTP response "Line too long" indicates that an email message line exceeds the allowed character limit (usually 998 characters). This is often due to missing CR/LF (carriage return/line feed) characters. It also suggests checking for issues when forwarding emails with attachments.