lmtpd NUL rejection

[John Alton Tamplin]

simon.brady at otago.ac.nz wrote:

>I've recently upgraded imapd from 1.5.19 to 2.1.11, and instead of having
>sendmail invoke deliver it now talks to lmtpd over a Unix socket. All is
>well, except that lmtpd is much more scrupulous about checking its input
>than deliver was - in the space of a week, it's detected three otherwise
>normal messages containing embedded NULs and has rejected them with DSN
>"554 5.6.0 Message contains NUL characters" (status
>IMAP_MESSAGE_CONTAINSNULL in imap/lmtpengine.c).
>
>OK, fair enough, except that sendmail responds to the bounce by trying to 
>copy the message to postmaster. Via lmtpd. Oops.
>
>Clearly the input is bad and lmtpd is justified in rejecting it. However,
>broken mail clients (or whatever - we haven't identified any common factor
>yet) are a fact of life, and having mail stuck in a non-delivery loop
>isn't very helpful for our users.
>
>What's the Right Thing to do here? Should sendmail (8.11.2) be configured
>to somehow report the failure without forwarding the message, or perhaps
>do NUL filtering on the fly? Or is there some way of configuring the lmtp
>mailer definition to get around this problem?
>
>And out of general curiosity, have other sites moving to lmtpd encountered 
>this, or are we just particularly weird?
>  
>
I noticed it here as well after switching from UW IMAP to Cyrus 2.1.11, 
and I am currently still running everything through a perl delivery 
program which does a number of clean-ups including stripping NUL 
characters. The problem is that a number of large mailing lists (such as 
some on Yahoo Groups) include NULs, so just dropping the mail wasn't an 
option.  Eventually, I want to get back to the stock deliver but I will 
need to patch it to include an option to strip NULs similarly (as well 
as other issues currently being handled in the perl script) before I can.

-- 
John A. Tamplin                               Unix System Administrator
Emory University, School of Public Health     +1 404/727-9931