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. [email protected] Can it be a problem of my mail server not configured correctly or is it a problem of the remote mail server ? Thanks
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.
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.
