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Home » OLD forums » Kerio Connect Multi-Server » problem with SMTP service: 451 4.3.2 Internal server error (SMTP not working)
problem with SMTP service: 451 4.3.2 Internal server error [message #123019] Wed, 22 July 2015 14:37 Go to next message
Michael Monnerie is currently offline  Michael Monnerie
Messages: 4
Registered: July 2015
Location: Korneuburg, Austria, Euro...
We want to run KCMS, but cannot start our tests because the SMTP service is not working:

# telnet 25
Connected to
Escape character is '^]'.
220 kc-frontend1 ESMTP ready
helo x
250 kc-frontend1
mail from: <x<_at_>>
250 2.0.0 OK
rcpt to: <michael.monnerie<_at_>>
451 4.3.2 Internal server error
Connection closed by foreign host.

What can we do here?

We had to change the IPs of the VMs, might that be the cause? If yes, how to solve?

Michael Monnerie

[Updated on: Wed, 22 July 2015 14:38]

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Re: problem with SMTP service: 451 4.3.2 Internal server error [message #123418 is a reply to message #123019] Tue, 11 August 2015 13:18 Go to previous message
Jakub Schwarzmeier, Kerio
Messages: 42
Registered: June 2010
Two things can, most usually, lead to this behavior:

1. You have only a single backend server deployed. At least two backend servers have to participate in the multi-server.
2. Master backend (= first backend) does not trust frontend queries. Check mailserver.cfg of the first backend for this setting:

<table name="Http">
<variable name="FrontendNetwork">Front-end nodes</variable>

<list name="IpAccessList">
<variable name="Name">Front-end nodes</variable>
<variable name="Value"></variable> <!-- Frontend IP has to be in this range. -->

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