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Re: SMTP Transferred-By-Reference

2007-11-17 15:03:22
On 2007-11-13 18:32:49 -0800, Douglas Otis wrote:
For ISP that host customers sending out a spam campaign, their  
servers may receive a temp error at that point in time.   
Unfortunately, this may cause some desired email to be delayed.  Once  
spamming from that server ceases, normal acceptance is restored.   
This dynamic reputation tactic blocks often more than twice the  
amount of spam stopped by static lists.  Graduated dynamic lists are  
available to suit the needs of different receivers.

Blocking an influx of spam using the temp error tactic frees up  
resources needed to process other (cleaner) sources of email.   
Simultaneously offering the TBR extension within the 451 4.7.8/9/10  
temp error would provide the transmitter a means to immediately  
complete their transaction by reverting to the TBR mode.  (Fewer  
transactions and less delay.)

If I understood this correctly an SMTP server supporting TBR may return
a 451 return code with any of the 4.7.8-10 enhanced status codes if it
is currently unable (or unwilling) to accept email content (e.g.,
because of high load, a full queue, etc.) but is able to accept a TBR
command. A client supporting TBR may then store the mail content on a
webserver and send the TBR command with the URI:

S: 250-SIZE 20971520
S: 250 TBR
C: MAIL FROM:<joe(_at_)example(_dot_)com> SIZE=10000000
S: 250 Ok
C: RCPT TO:<jane(_at_)example(_dot_)net>
S: 250 Ok
S: 451 4.7.10 Load too high - try TBR HTTPS mode

(client saves the 10 MB message on

C: TBR 0
S: 250 Ok

I didn't understand this while reading the draft. You may want to
clarify section 6.


   _  | Peter J. Holzer    | It took a genius to create [TeX],
|_|_) | Sysadmin WSR       | and it takes a genius to maintain it.
| |   | hjp(_at_)hjp(_dot_)at         | That's not engineering, that's art.
__/   | |    -- David Kastrup in comp.text.tex

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