postfix open relay
Hi redhat support,
i just would like to ask how can i check or verify that open relay is active in our smtp server.
thanks.
Responses
The basic steps are:
Connect to SMTP server from an external host (ie. outside your local network that hasn't been configured to allow relaying) and attempt to send an email to a domain that your postfix server doesn't accept mail for (ie. it's not your domain).
Here is an example attempt to send from your mail server to a third party destination:
telnet smtp.yourdomain.com 25 (your externally exposed SMTP server)
helo yourdomain.com
mail from: something@yourdomain.com
rcpt to: something@notyourdomain.com
You should now get a "554 Relay access denied", if you get a "250 Ok" or similar, your server is going to relay.
The 'rcpt to' portion should only accept mail addressed to addresses @yourdomain.com
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