[Dovecot] Error with Dovecot LDA when using recipient address misses user part

[Nikolaos Milas]

Hi,

We are using Postfix 2.8.3 with Dovecot 2.0.13 on CentOS 5.6.

The problem we have is that sometimes, due to mail sender's error when 
composing a message, the sender attempts to send an email to "@noa.gr" 
(without specifying the user part of the address). This results in a 
Postfix error due to Dovecot LDA use:

Jun 22 21:05:31 vmail postfix/pipe[31862]: CC89FC4D210: to=<@noa.gr>, 
relay=dovecot, delay=0.41, delays=0.24/0.013/0/0.15, dsn=5.3.0, 
status=bounced (command line usage error. Command output: 
/usr/libexec/dovecot/dovecot-lda: option requires an argument -- d 
Usage: dovecot-lda [-c <config file>] [-a <address>] [-d <username>] [-p 
<path>]                    [-f <envelope sender>] [-m <mailbox>] [-e] [-k] )

Postfix master.cf is configured as:

dovecot   unix  -       n       n       -       -       pipe
   flags=DRhu user=vmail:vmail argv=/usr/libexec/dovecot/dovecot-lda -f 
${sender} -d ${user}

Obviously this happens because in this case there is no ${user} data.

My question is: Can we somehow configure things in a way so as to avoid 
this error when someone sends an email with blank sender data? Can 
Dovecot provide some meaningful message to postfix (like "No user 
specified") instead of failing with a "command line usage error"?

Thanks,
Nick

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