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What is Quoted-printable (QP) encoding?
Quoted-printable (QP) encoding is a method used to represent non-printable or special characters in a format that can be used within email messages. It is particularly useful when sending emails that contain characters that are not a part of the ASCII character set or have special significance in email formatting.
Why is QP encoding important in sending emails?
When sending emails, it is essential to consider the limitations of the underlying communication protocols and the character sets that can be reliably transmitted. The ASCII character set, which consists of 128 standard characters, is usually the safest and most widely supported option for email communication.
However, when a message includes characters outside of the ASCII character set, such as non-English alphabets or specific symbols, the characters need to be encoded to ensure their correct transmission. This is where QP encoding comes into play.
How does QP encoding work?
QP encoding follows a simple principle: it represents non-printable or special characters through a combination of ASCII characters, making it suitable for use in email headers and bodies.
The encoding process involves replacing each non-printable or special character with a “=” sign, followed by the two-digit hexadecimal representation of its ASCII code. For example, if a character has the ASCII code of 173, it would be encoded as “=AD”.
Additionally, some characters have special significance in email formatting, such as the period (“.”) at the beginning of a line. To avoid confusion, QP encoding represents such characters using the “=” sign followed by their ASCII code. For instance, a period at the start of a line becomes “=2E”.
Example of QP encoding:
Let’s say we have a message that includes the following sentence:
Don’t forget the café!
In QP encoding, it would be represented as:
Don’t forget the =E9caf=E9!
Here, “=E9” represents the accented “e” in “café” using its hexadecimal ASCII code.
In conclusion, QP encoding plays a crucial role in ensuring reliable transmission of email messages containing non-ASCII characters or characters with special significance in email formatting. By encoding these characters in a standardized and recognizable format, QP encoding ensures that the email content is correctly understood and displayed by the recipient’s email client.
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