Why are there invalid characters in my email subject line?

Email marketer from Mailjet explains that invalid characters in email subject lines often result from incorrect character encoding. They recommend using UTF-8 encoding for broader compatibility and suggest checking the email client or platform's encoding settings.

Email marketer from Campaign Monitor explains that using special characters not supported by some email clients, and double-check encoding settings to ensure compatibility across various platforms.

Email marketer from Email on Acid explains that when including symbols and special characters it's key to ensure that they are correctly encoded for email clients and that the encoding used is UTF-8.

Email marketer from Reddit mentions that issues with displaying special characters correctly depend on the email client and the encoding used when composing the email. They suggest testing with different encoding options (like UTF-8) and ensuring the client supports it.

Email marketer from Litmus explains that when using special characters or symbols in subject lines, ensure the characters are properly encoded in UTF-8. If they are copied from external sources they may not be encoded properly so it's best to manually type or recode special characters.

Email marketer from Stack Overflow shares that issues with garbled characters in subject lines can arise from using the wrong character set when composing the email. They recommend checking if the email is sent as UTF-8 and suggest encoding the subject line correctly before sending.

Email marketer from ActiveCampaign explains to avoid encoding issues, always use UTF-8 encoding. Also check for unsupported special characters. If the issue still persists then contact support.

Expert from Word to the Wise explains that incorrect handling of character sets when composing emails can result in invalid characters. Laura Atkins recommends using UTF-8 character sets and verifying that the email client and server support it, to avoid display issues across different receiving systems.

Expert from Email Geeks provides a command to decode and examine the subject line's hexadecimal representation, revealing a trailing zero byte.

Expert from Email Geeks explains that the base64 encoded subject line contains a trailing zero byte, which could be causing issues with some mail servers.

Expert from Spam Resource shares that the use of non-ASCII characters without proper encoding can result in display issues, especially in older email clients. They recommend using UTF-8 and testing across different email clients to ensure proper rendering.

Documentation from Microsoft explains that incorrect character sets or code pages used when composing an email can lead to invalid characters. They advise ensuring the correct character set is selected in the email client or program being used.

Documentation from ietf.org details the standards for representing non-ASCII text in email headers, stating that invalid characters may appear if the subject line isn't properly encoded according to RFC 2047. It highlights the importance of using 'encoded-words' to represent characters outside the ASCII range.

Documentation from Oracle explains that certain email servers only support 7-bit ASCII. To encode other characters, MIME headers are necessary for the email to be correctly delivered and displayed by the receiver's email application.

Documentation from Python Docs details the base64 content transfer encoding scheme. It mentions that sometimes email clients can throw an error when characters in a subject line are not appropriately encoded, so base64 is useful for encoding arbitrary sequences of octets in a form that is designed to be both readable by humans and reliably transmittable by mail systems.

Documentation from Unicode Consortium explains that one cause of invalid characters is using Unicode characters that are not supported by the email client or system. It advises to ensure compatibility by sticking to widely supported Unicode ranges or using appropriate fallbacks.