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Old 13th November 2007, 09:18
vaio1 vaio1 is offline
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Default Destination mail server ... is it really not reachable?

Hi guys,
I suppose that some server are not reachable for some particular mail server configuration.

I need to understand why this message appears:

Code:
This is an automatically generated Delivery Status Notification.

Unable to deliver message to the following recipients, due to being unable to connect successfully to the destination mail server.

       emailtest@flashidiomas.com.br
Can it be a problem of my mail server not configured correctly or is it a problem of the remote mail server ?

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Old 13th November 2007, 16:21
Hawker Hawker is offline
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If the error doesn't happen on every mail sent, then it's not a problem with your setup.

An unable to connect error can be a multitude of things, including your IP address being blocked by a firewall rule. Personally I drop (not reject) connections from many IP addresses which would give you the error you have.
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Old 13th November 2007, 16:24
vaio1 vaio1 is offline
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How can I drop and not reject, the connections from many IP addresses ?

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Old 13th November 2007, 16:33
Hawker Hawker is offline
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Directly through iptables or if you're using Bastille firewall by adding this to etc/Bastille/firewall.d/post-rule-setup.sh...

Code:
/sbin/iptables -I INPUT -p tcp -s IPADDRESS --dport PORTNUMBER -j DROP
Then /etc/init.d/bastille-firewall restart

The options for -j are ACCEPT, DROP, REJECT and RETURN (jump to another chain in iptables).

Be carefull you can block more than you want to. For example I ACCEPT mail on port 25 from howtoforge.com but DROP all other ip addresses in their CIDR (81.0.0.0/8) that attempt to access port 25.

Last edited by Hawker; 13th November 2007 at 16:48.
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Old 13th November 2007, 16:57
edge edge is offline
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Could also be a bad configured DNS server.
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