zemon@felix.UUCP (01/29/87)
I started playing with the sendmail stuff which came with
4.3 BSD and had a user point out a rude surprise. He tried
sending something like this
To: felix!zemon
-------
foo
.
bar
and received
To: felix!zemon
From: fritz!someone
--------
foo
The SMTP protocol seems to have ended the message at the
dot and ignored the rest.
I'm using the lanroot.mc and lanleaf.mc configuration files
in the no-named directory. The message originated at a
leaf site and was sent to the root site (felix), where
"zemon" is aliased to "zemon@fritz". Using the MH send
command with the verbose and watch options, you see that
sendmail sets up a SMTP connection and the receiver says
that the message text should be sent with the end indicated
by a line with a single period on it. Well, the receiver
keeps his word and ignores the rest of the message. This
is probably a bug given the following....
Now the strangeness. Sending the same message from kelly,
another leaf site, to fritz using the address "zemon@fritz"
instead of "fritz!zemon" works correctly. But sending it
from kelly using address "zemon@felix" also fails by the
time the message is finally delivered to fritz.
So what's going on? Is this a bug in the protocol? Has
this been solved? Shouldn't these things be escaped like
"From" lines? Or something?
--
-- Art Zemon
FileNet Corporation
Costa Mesa, California
...! {decvax, ihnp4, ucbvax} !trwrb!felix!zemonguy@gorodish.UUCP (01/30/87)
>So what's going on? Is this a bug in the protocol? No, it's a feature of the protocol. See RFC 821, "Simple Mail Transfer Protocol". >Has this been solved? Shouldn't these things be escaped like >"From" lines? Yes. See RFC 821, Page 41 (page 47 in the "Internet Mail Protocols" document): 4.5.2 TRANSPARENCY Without some provision for data transparency the character sequence "<CRLF>.<CRLF>" ends the mail text and cannot be sent by the user. In general, users are not aware of such "forbidden" sequences. To allow all user compsed text to be transmitted transparently the following procedures are used. 1. Before sending a line of mail text the sender-SMTP checks the first character of the line. If it is a period, one additional period is inserted at the beginning of the line. 2. When a line of mail text is received by the receiver-SMTP it checks the line. If the line is composed of a single period it is the end of mail. If the first character is a period and there are other characters on the line, the first character is deleted. The feature described in 1. is enabled on a per-mailer basis in "sendmail" by turning on the "X" flag for the mailer. The feature described in 2. is enabled for all mailers running in "SMTP mode"; i.e., all mailers started off by somebody connecting to the "sendmail" daemon's SMTP port. When "sendmail" is receiving its message from some source other than an SMTP connection - e.g., reading the message being handed to it on its standard input by "Mail" - it will treat "." on a line by itself as the end of the message body. If you turn on the "ignore dots in messages" flag (by passing the "-Oi" flag as an argument to "sendmail") it will not treat periods specially in any way. "/bin/mail", prior to the advent of "delivermail", accepted either a "." on a line by itself or an EOF as the end of a message. The version of "/bin/mail" that worked with "delivermail" and works with "sendmail" just turns around and fairly quickly calls "delivermail" or "sendmail" and lets it collect the body of the message. As such, it doesn't want to use the "-i" flag to "delivermail" or the "-Oi" flag to "sendmail". "/usr/ucb/mail" permits you to override this, but it collects the mail itself and sends it off to "delivermail" or "sendmail" when it's done. As such, it passes the "-i" flag to *both* of them ("-i" is an undocumented synonym for "-Oi" in "sendmail", left around for compatibility with "delivermail"). I assume MH also does the right thing; i.e., it collects the message itself and passes "-i" or "-Oi" to "sendmail". The fact that the message gets correctly delivered on some occasions supports this conclusion, unless MH does something different with "!" and "@" addresses (in which case it should consider leaving that up to "sendmail", considering that's its job). When you do these tests, does a recipient address *ever* resolve to a non-IPC mailer? If so, make sure that if that mailer ever runs "sendmail" it runs it with "-i" or "-Oi". I presume you have added stuff to map UUCP addresses to local addresses, so that "fritz!zemon" gets delivered using SMTP eventually. Make sure this isn't somehow causing the problem; does mail from "kelly" to "fritz!zemon" *ever* pass through the hands of UUCP? If so, make sure it doesn't do so. Also, if you've changed *any* of the configuration files, make sure you don't run *any* IPC mailer without having the "X" flag set for the mailer.
meissner@dg_rtp.UUCP (01/30/87)
In article <2195@felix.UUCP> zemon@felix.UUCP (Art Zemon) writes: > > The SMTP protocol seems to have ended the message at the > dot and ignored the rest. This is a "feature" of sendmail. The original UNIX mailer /bin/mail had this feature also. I suspect the reason /bin/mail had it, was because UNIX was developed in the days of ASR-33 Teletypes, which was hard to use control characters. -- Michael Meissner, Data General ...mcnc!rti-sel!dg_rtp!meissner
chris@mimsy.UUCP (Chris Torek) (02/01/87)
In article <2195@felix.UUCP> zemon@felix.UUCP (Art Zemon) writes: >I started playing with the sendmail stuff which came with 4.3BSD .... >The SMTP protocol seems to have ended the message at the >dot and ignored the rest. The SMTP protocol is defined as doing this. Dots at the beginnings of lines must be quoted by doubling. Sendmail's IPC mailer does this when speaking SMTP to another mailer. If you are feeding input to sendmail (e.g., via UUCP) and want it NOT to terminate at a line that reads `.', run `sendmail -i'. The 4.3 rmail presumably does this (I have not checked). -- In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7690) UUCP: seismo!mimsy!chris ARPA/CSNet: chris@mimsy.umd.edu