Postfix- open relay. How to configure so it is not?
Solution 1
mynetworks must only contain trusted users that can use the server to relay mails to other domains - otherwise, as you've found, it's an open relay. You might want to set it to 192.168.0.0/16, 10/8 or 172.16.0.0/12 if using RFC 1918 addresses on your internal network.
The settings that control whether people can send mail to your server include mydestination and virtual_mailbox_domains - read the docs here or here.
Solution 2
The problem that opens you up is the
mynetworks = 0.0.0.0/0
Cause somewhere below you probably have it listed in
smtpd_recipient_restrictions = ... permit_mynetworks ...
If you need to be able to send email from any ip then you just look at enabled a user/password to send email which the common one is sasl
Solution 3
As documented at http://www.postfix.org/postconf.5.html#mynetworks :
mynetworks (default: see "postconf -d" output)
The list of "trusted" remote SMTP clients that have more privileges than "strangers".In particular, "trusted" SMTP clients are allowed to relay mail through Postfix.
See the smtpd_recipient_restrictions parameter description in the postconf(5) manual.
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Updated on September 18, 2022Comments
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Lock over 1 year
I have setup Postfix but am having trouble with the setup.
Whenever I used to send emails to the server, it reject my mails saying 'Relaying Denied', so I changed the following in
main.cf
:mynetworks = 0.0.0.0/0 mynetworks_style = subnet
I can now send email and it works, but MX tests say that it is an open relay (obviously unintended).
How can I resolve this? I obviously want anybody to be able to email my domain, but I'm unsure of the configuration.
I know I can change the
mynetworks
, but then doesn't this restrict who CAN email to the server?-
nickgrim over 11 yearsAre you trying to relay mail through this server, or to deliver mail to this server?
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adaptr over 11 yearsMakes no difference with respect to this issue, since an open relay is an open relay. Email is not a trivial undertaking.
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adaptr over 11 yearsmydestination, relay_domains, and virtual_[alias|mailbox]_maps. NOT virtual_[alias|mailbox]_DOMAINS.