Re: 501 Syntax error: Empty email address.

[Rolando Guaracio]

Thank you Viktor!


On 10/29/2015 12:17 PM, Viktor Dukhovni wrote:

On Thu, Oct 29, 2015 at 12:05:55PM -0300, Rolando Guaracio wrote:

    mta4: This MTA send messages to Internet.
    mta4 relay the NDN to Internet ...

    Oct 29 08:20:56 mta4 postfix/smtpd[19077]: 980A1A0A49:
       client=mta1[10.20.152.148]
    Oct 29 08:20:56 mta4 postfix/cleanup[19079]: 980A1A0A49:
       message-id=[10]<20151029112056.9234540...@mta1.domain.com>
    Oct 29 08:20:56 mta4 postfix/qmgr[30576]: 980A1A0A49: from=<>,
       size=7585, nrcpt=1 (queue active)
    Oct 29 08:20:56 mta4 postfix/smtp[18973]: 980A1A0A49:
       to=<sen...@example.com>, relay=mx1.example.com[x.x.x.x]:25,
       delay=0.04, delays=0.02/0/0.01/0, dsn=5.0.0, status=bounced (host
       mx1.example.com[x.x.x.x] said: 501 Syntax error: Empty email address.
       (in reply to MAIL FROM command))
    Oct 29 08:20:56 mta4 postfix/qmgr[30576]: 980A1A0A49: removed

As expected, the erroneous "Syntax error:" message is generated by
the MX host of the original sender's domain.  That domain refuses
bounce messages.  Bounce messages MUST be sent with an empty sender
address to avoid mail loops.  There is no other way to send bounces.

    So, the sender never have a notification that his mail was bounced
    because the account is over quota.

The sender's domain has decided they don't want your bounces.

    Can I resolve this with some configuration with the NDN messages? For
    example send it without null from.

The best thing to do is to configure your inbond MX host to reject
mail for users who are over quota, by periodically updating a suitable
table that lists overquote addresses.

     main.cf:
        indexed = ${default_database_type}:${config_directory}
        transport_maps = ${indexed}transport

     transport:
        overquota@your-domain.example   error:5.2.2 Mailbox full

or

     main.cf:
        indexed = ${default_database_type}:${config_directory}
        smtpd_recipient_restrictions =
            permit_mynetworks,
            reject_unauth_destination,
            check_recipient_access ${indexed}rcpt-access

     rcpt-access:
        overquota@your-domain.example   552 5.2.2 Mailbox full

That way, you won't be sending nearly as much backscatter.  Also
give users larger disk quotas.  Running out of space should be
rare.