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I have to check if my server (SUSE 11) is used as an SMTP Open Mail Relay and, if so, block this unwanted feature.
I check /etc/postfix/main.cf and all relay's related variables are commented :
#relayhost = $mydomain
#relayhost = [gateway.my.domain]
#relayhost = [mailserver.isp.tld]
#relayhost = uucphost
#relayhost = [an.ip.add.ress]
Could someone help me?
An open relay doesn't have anything to do with relay options. To test it simply establish a connection and try to send an e-mail to a foreign domain. If you need to do this due to receiving a report that your server is an open relay/you're on a blacklist check your mail queue length.
– Seth – 2019-09-18T09:01:20.680You need to check, if unauthorized users can send mail via your system. Usually your server on should accept mail 1) to local users 2) from authorized users to anyone 3) possibly from trusted IPs to anyone. Otherwise it should reject the mail. When your server can be used to send mail to anyone, it is called an open relay and will sooner or later relay spam, when automated spam bots find it and use it. – allo – 2019-09-18T09:19:43.393