Garbled text can occur in emails if the recipient's email program cannot understand the character encoding. While emails were originally specified to use only US-ASCII characters to avoid this issue, MIME allows encoding of non-ASCII text into ASCII. As long as the charset and encoding are correctly specified in the email headers, garbled text can be avoided even when using multi-byte character sets. However, some email programs still have bugs that can cause them to mistake the character set in some situations.

1. Garbled text
in email
SEG
Satoshi Tashiro

2. Agenda
- What is a garbled text
- Why garbled text happened
- Email text specifications
- MIME < Let them eat cake >
- MIME and Character code

3. What is a garbled text

4. If recipient mailer can’t understand character
code, garbled text happen.
Why garbled text happened ?
written by Mars Language Terellian mailer can not understand

5. If you use US-ASCII, almost recipient mailer
can understand character code.
You do not need to get garbled text.
Why garbled text happened ?
HELLO!
HELLO!

6. Email text specifications
Oh! by the way, RFC says…
You can use US-ASCII character only.
Multibyte character can not use in email.
RFC-5321 (2.3.1. Mail Objects)
The content is textual in nature, expressed using the US-ASCII repertoire.

7. Expressed using the US-ASCII repertoire.
Garbled text in email not happened.
We are happy !
That’s all !
Thank you !!

9. We are multibyte character

10. http://en.wikipedia.org/wiki/Language

11. We are multibyte character
What should we do ?
(´・ω・`)

12. Don’t worry, we have a MIME
Multipurpose Internet Mail Extensions (MIME) is an
Internet standard that extends the format of email to
support:
- Text in character sets other than ASCII
- Non-text attachments
- Message bodies with multiple parts
- Header information in non-ASCII character sets

13. MIME < Let them use US-ASCII >
Email should be ASCII character.
=> Encode to ASCII !!
non-ASCII -> ASCII
かめはめ波 -> 44GL44KB44Gv44KB5rOiC

14. If you announce charset and
encoding correctly, we don’t get
garbled text
Written by UTF-8 and
MIME(Base64) encode. Base64 decode and
reading UTF-8
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: base64
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: base64
We are happy !
Thank you !!

15. It is regrettable to say this, but…
Now, your mailer has auto detect function to charset.
Therefor...
- Gmail occasionally mistakes Japanese and Chinese
- Microsoft Outlook also the same
- If attached csv file, Gmail misconstrued to US-ASCII
These are bug of mailer. but not repaired...