RFC 1555

RFC 1555: Hebrew Character Encoding for Internet Messages 🎀

Okay bestie, this is RFC 1555 from the Network Working Group, and it's giving Hebrew in email 🇮🇱✨ It's Category: Informational, dated December 1993. Hank Nussbacher (Israeli Inter-University Computer Center) and Y. Bourvine (Hebrew University) wrote it 🧚 Its title block doesn't list anything it obsoletes or updates 💜

Status of This Memo 🌸

This memo gives info to the Internet community, but it does NOT specify an Internet standard of any kind 🙈 Distribution of this memo is unlimited 🦋

Abstract 💖

This doc explains the encoding used in electronic mail [RFC822] to send Hebrew. The standard uses MIME [RFC1521] and ISO-8859-8, and it's honestly so clean 💅

Description 🌈

Okay so, all Hebrew text sent over email must first be translated into ISO-8859-8, and then encoded with either Quoted-Printable (preferable) or Base64, as defined in MIME 🫶

Here's the table of the four most common Hebrew encodings, and it's a whole vibe 📊

                   PC    IBM     PC     ISO
       Hebrew                           8859-8
       letter     8-bit         7-bit   8-bit
                  Ascii  EBCDIC Ascii   Ascii
       ---------- -----  ------ -----   ------
       alef        128     41    96     224
       bet         129     42    97     225
       gimel       130     43    98     226
       dalet       131     44    99     227
       he          132     45   100     228
       vav         133     46   101     229
       zayin       134     47   102     230
       het         135     48   103     231
       tet         136     49   104     232
       yod         137     51   105     233
       kaf sofit   138     52   106     234
       kaf         139     53   107     235
       lamed       140     54   108     236
       mem sofit   141     55   109     237
       mem         142     56   110     238
       nun sofit   143     57   111     239
       nun         144     58   112     240
       samekh      145     59   113     241
       ayin        146     62   114     242
       pe sofit    147     63   115     243
       pe          148     64   116     244
       tsadi sofit 149     65   117     245
       tsadi       150     66   118     246
       qof         151     67   119     247
       resh        152     68   120     248
       shin        153     69   121     249
       tav         154     71   122     250

Note: All values are in decimal ASCII except for the EBCDIC column, which is in hexadecimal. 🔥

ISO 8859-8 8-bit ASCII is also known as IBM Codepage 862 👑

Now the directionality bit 🧠 The default directionality of the text is visual. So the Hebrew gets encoded left to right (even though you type it right to left) and it's sent left to right through the standard MIME mechanisms. Other ways to control directionality exist too, and they're covered in the complementary RFC 1556, "Handling of Bi-directional Texts in MIME" ✨

All the chat about Hebrew in email, plus Hebrew in other TCP/IP protocols, happens on the ilan-h@vm.tau.ac.il list. To subscribe, send mail to listserv@vm.tau.ac.il with one line of text like this:

                 subscribe ilan-h firstname lastname

MIME Considerations 🦋

Mail that contains Hebrew needs at least these MIME headers, no exceptions 💅

      MIME-Version: 1.0
      Content-type: text/plain; charset=ISO-8859-8
      Content-transfer-encoding: BASE64 | Quoted-Printable

Users should keep their text within 72 columns so email quoting works, since each line gets a ">" in front 💖 Also, heads up: not every MIME implementation handles quoting properly, so quoting Hebrew email might cause problems 😭

Later on, when every email system does fully transparent 8-bit email as defined in RFC 1425 and RFC 1426, this standard will become partially obsolete 🔮 The "Content-type:" field will still be needed, and so will directionality (which might be implicit for 8BIT, but that's a future discussion). The "Content-transfer-encoding" will switch to 8BIT instead of Base64 or Quoted-Printable 🌸

Optional 🍓

It is recommended, though not required, to support Hebrew encoding in mail headers as specified in RFC 1522. Specifically, Q-encoding is the default for Hebrew in Internet mail headers, not B-encoding 🫶

Caveats ⚠️

Inside Israel there are more than 40 Listserv lists that are about to start using Hebrew for part of their conversations 🇮🇱 Normally, Listserv delivers list mail with a "shortened" header, one that leaves out the extra MIME headers. That means the MIME encoding stays intact and the user agent's decoding software can't interpret the mail 😩 Each user can customize how Listserv delivers their mail. For lists that contain Hebrew, users should send this command to Listserv:

                         set listname full

Here, listname is the name of the list you want to get full, unabridged headers. It updates your private entry, and every mail from that list after that comes with full RFC822 headers, MIME headers included 🎀

Also, Listserv usually keeps automatic archives of every posting to a list. Those archives, in the file listname LOGyymm, don't include the MIME headers, so all the encoding info gets lost. That's a limitation of the Listserv software, not something we can fix 💀

Heads up: the archive files drop the MIME headers, so encoding info is lost there. This is a Listserv software limitation.

Example 🧚

Here's a short example of Quoted-Printable encoded Hebrew email 💌

   Date:         Sun, 06 Jun 93 15:25:35 IDT
   From:         Hank Nussbacher <HANK@VM.BIU.AC.IL>
   Subject:      Sample Hebrew mail
   To:           Hank Nussbacher <Hank@BARILVM>,
                 Yehavi Bourvine <yehavi@hujivms>
   MIME-Version: 1.0
   Content-Type: Text/plain; charset=ISO-8859-8
   Content-Transfer-Encoding: QUOTED-PRINTABLE

   The end of this line contains Hebrew            .=EC=E0=F8=F9=E9 =F5=
   =F8=E0=EE =ED=E5=EC=F9


   Hank Nussbacher                                  =F8=EB=E1=F1=E5=
   =F0 =F7=F0=E4

Acknowledgements 🫶

Huge thanks to Rafi Sadowsky and Nathaniel Borenstein for all their help 💜

References 📚

   [ISO-8859] Information Processing -- 8-bit Single-Byte Coded
              Graphic Character Sets, Part 8: Latin/Hebrew alphabet,
              ISO 8859-8, 1988.

   [RFC822]   Crocker, D., "Standard for the Format of ARPA Internet
              Text Messages", STD 11, RFC 822, UDEL, August 1982.

   [RFC1425]  Klensin, J., Freed N., Rose M., Stefferud E., and
              D. Crocker, "SMTP Service Extensions", RFC 1425,
              United Nations University, Innosoft International, Inc.,
              Dover Beach Consulting, Inc., Network Management
              Associates, Inc., The Branch Office, February 1993.

   [RFC1426]  Klensin, J., Freed N., Rose M., Stefferud E., and
              D. Crocker, "SMTP Service Extension for 8bit-MIME
              Transport", RFC 1426, United Nations University, Innosoft
              International, Inc., Dover Beach Consulting, Inc., Network
              Management Associates, Inc., The Branch Office, February
              1993.

   [RFC1521]  Borenstein N., and N. Freed, "MIME (Multipurpose
              Internet Mail Extensions) Part One: Mechanisms for
              Specifying and Describing the Format of Internet Message
              Bodies", Bellcore, Innosoft, September 1993.

   [RFC1522]  Moore K., "MIME Part Two: Message Header Extensions for
              Non-ASCII Text", University of Tennessee, September 1993.

Security Considerations 🔒

Security issues are not discussed in this memo. So if you came here for security stuff, it's not in here 🙈

Authors' Addresses 💌

   Hank Nussbacher
   Computer Center
   Tel Aviv University
   Ramat Aviv
   Israel

   Fax: +972 3 6409118
   Phone: +972 3 6408309
   EMail: hank@vm.tau.ac.il


   Yehavi Bourvine
   Computer Center
   Hebrew University
   Jerusalem
   Israel

   Phone: +972 2 585684
   Fax:   +972 2 527349
   EMail: yehavi@vms.huji.ac.il