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loicnestler/check-mailserver-for-openrelay.txt

Created February 7, 2021 19:11
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Check mail server for OpenRelay
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check-mailserver-for-openrelay.txt
# Stolen from https://github.com/Mailu/Mailu/issues/1370#issuecomment-592447023
# $YOUR_PUBLIC_SERVER_IP = your mail server IP
# $YOUR_PUBLIC_SERVER_DOMAIN = your mail server domain (mail.example.org)
# $A_MAIL_NOT_MANAGED_BY_YOUR_SERVER = some mail address that is not managed by your mail server (for example a @gmail address)
$ nc -v $YOUR_PUBLIC_SERVER_IP
Ncat: Version 7.80 ( https://nmap.org/ncat )
Ncat: Connected to $YOUR_PUBLIC_SERVER_IP:25.
220 $YOUR_MAIL_SERVER_DOMAIN ESMTP ready
HELO $YOUR_MAIL_SERVER_DOMAIN
250 $YOUR_MAIL_SERVER_DOMAIN
MAIL FROM: $A_MAIL_NOT_MANAGED_BY_YOUR_SERVER
250 2.0.0 OK
RCPT TO: $ANOTHER_MAIL_NOT_MANAGED_BY_YOUR_SERVER
554 5.7.1 <$ANOTHER_MAIL_NOT_MANAGED_BY_YOUR_SERVER>: Relay access denied
# The output of line 14 is the important one. If it says "Relay access denied" than your server does not support OpenRelay (which is good for most purposes).
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