Re: [exim] MessageLabs 554 SMTP synchronisation error

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Szerző: Carsten Koch-Mauthe
Dátum:  
Címzett: exim-users
Tárgy: Re: [exim] MessageLabs 554 SMTP synchronisation error
Hi,

Am Dienstag, 12. Juli 2005 00:50 schrieb Jakob Hirsch:
> Giuliano Gavazzi wrote:
> >>> 4) From a supposed print screen I see that they get this [a 554
> >>> error] right after the 'Escape character is...' message with no
> >>> greeting message displayed.
>
> Maybe their telnet client send something in order to negotiate some
> connection parameter. They should try netcat, which has not such hidden
> magic.


Try this:

=== Schnipp ===
smtp_enforce_sync         Use: main   Type: boolean             Default: true


    The SMTP protocol specification requires the client to wait for a response
    from the server at certain points in the dialogue. Without PIPELINING
    these synchronization points are after every command; with PIPELINING they
    are fewer, but they still exist.


    Some spamming sites send out a complete set of SMTP commands without
    waiting for any response. Exim protects against this by rejecting a
    message if the client has sent further input when it should not have. The
    error response '554 SMTP synchronization error' is sent, and the connec-
    tion is dropped. Testing for this error cannot be perfect because of
    transmission delays (unexpected input may be on its way but not yet
    received when Exim checks). However, it does detect many instances.


    The check can be globally disabled by setting "smtp_enforce_sync" false.   
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    If you want to disable the check selectively (for example, only for        
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    certain hosts), you can do so by an appropriate use of a "control"         
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    modifier in an ACL (see section 39.18). See also                           
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    "pipelining_advertise_hosts".
=== Schnapp ===


Gruss
Carsten