TCP IP Illustrated

1993b this allows the client to add the keyword body

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Unformatted text preview: starts to send it. This command was added since the size of Internet mail messages is growing, with the support for message content other than ASCII lines (i.e., images, audio, etc.). The next host also supports ESMTP. Notice that the 250 reply specifying that the SIZE keyword is supported contains an optional argument. This indicates that this server will accept a message size up to 461 Mbytes. sun % telnet ymir.claremont.edu 25 220 ymir.claremont.edu -- Server SMTP (PMDF V4.2-13 #4220) ehlo sun.tuc.noao.edu 250-ymir.claremont.edu file:///D|/Documents%20and%20Settings/bigini/Doc...omenet2run/tcpip/tcp-ip-illustrated/smtp_sim.htm (15 of 23) [12/09/2001 14.47.52] Chapter 28. SMTP: Simple Mail Transfer Protocol 250-8BITMIME 250-EXPN 250-HELP 250-XADR 250 SIZE 461544960 The keyword 8BITMIME is from RFC 1426 [Klensin et al. 1993b]. This allows the client to add the keyword BODY to the MAIL FROM command, specifying whether the body contains NVT ASCII characters (the default) or 8-bit data. Unless the client receives the 8BITMIME keyword from the server in response to a EHLO command, the client is forbidden from sending any characters other than NVT ASCII. (When we talk about MIME in this section, we'll see that an 8-bit SMTP transport is not required by MIME.) This server also advertises the XADR keyword. Any keyword that begins with an X refers to a local SMTP extension. The next server also supports ESMTP, advertising the HELP and SIZE keywords that we've already seen. It also supports three local extensions that begin with an X. sun % telnet dbc.mtview.ca.us 25 220 dbc.mtview.ca.us Sendmail 5.65/3.1.090690, it's Mon, 2 Aug 93 15:48:50 -0700 ehlo sun. tuc.noao.edu 250-Hello sun.tuc.noao.edu, pleased to meet you 250-HELP 250-SIZE 250-XONE 250-XVRB 250 XQUE Finally we see what happens when the client tries to use ESMTP by issuing the EHLO command to a server that doesn't support it. sun % telnet relay1.uu.net 25 220 relay1.UU.NET Sendmail 5.61/UUNET-internet-primary ready at Mon, 2 Aug 9...
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This test prep was uploaded on 04/04/2014 for the course ECE EL5373 taught by Professor Guoyang during the Spring '12 term at NYU Poly.

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