<<<No Message Collected>>> NOW FIXED!

[Spicer, Kevin]

I have finally tracked down the source of this error & the fix is working fine.  Even if you haven't seen this error yourself you probably want to read this.

The problem is caused by a connecting smtp server issuing at ETRN command (our exchange server was doing this, although I'm told its not the default behavior for exchange).  The ETRN command causes the queue only sendmail process to attempt to deliver all the mail for the specified domain direct from mqueue.in.  This is a feature of sendmail, and is turned on by default!  This results in one of four behaviours (depending on when sendmail / mailscanner 'see' a message) as follows (I posted this bit previously)...

>>  1) Mailscanner sees the mail quickly and processes it normally.

>>  2) Sendmail sees the mail quickly and delivers it without being scanned.

>>  3) Both see it around the same time, mailscanner trys to process and sendmail trys to 
>>  deliver, but mailscanner picks up the body before sendmail causing sendmail to replace 
>>  the body with '<<<No Message Collected>>>' and log an error.  The outgoing sendmail 
>>  also attempts to deliver the message (after scanning) but it is silently discarded by 
>>  the Exchange server which incoming mail is forwarded to [guessing a bit on the exact
>>  behaviour of exchange, but sendmail seems to manage to deliver it twice].

>>  4) Both see it around the same time, mailscanner trys to process and sendmail trys to 
>>  deliver, but sendmail gets the body first causing mailscanner to log an error to the 
>>  console when it trys to cat the file.

On low loads 1 is the normal, as the load increases  you start to see more of 2,3 and 4

I fixed this by adding noetrn to confPRIVACY_FLAGS in sendmail.mc and rebuilding sendmail.cf, however Julian has pointed out that it can also be disabled by adding 

-OPrivacy_Options=noetrn

to the incoming sendmail command in the init script.

Because sendmail isn't fussy about who issues the ETRN command it is possible that a third party could issue an ETRN command to your sendmail, specifying your domain and cause mail to be delivered without being scanned.  I'd therefore suggest that everyone disables ETRN as detailed above.

I understand from Julian that he has added this to the news section on the site and has updated the init script on the next version.

Thanks to everyone who posted helpful suggestions.



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