{"id":981,"date":"2017-06-26T05:45:41","date_gmt":"2017-06-26T02:45:41","guid":{"rendered":"https:\/\/community.virtono.com\/?p=981"},"modified":"2017-06-26T05:52:27","modified_gmt":"2017-06-26T02:52:27","slug":"con%ef%ac%81guring-and-securing-your-postfix-mail-relay-policy","status":"publish","type":"post","link":"https:\/\/www.virtono.com\/community\/knowledgebase\/con%ef%ac%81guring-and-securing-your-postfix-mail-relay-policy\/","title":{"rendered":"Con\ufb01guring and Securing Your Postfix Mail Relay Policy"},"content":{"rendered":"

Post\ufb01x\u2019s relaying policy (allowing users to send mail through the mail server) is dictated by default via the mynetworks parameter. The mynetworks parameter tells Post\ufb01x what networks or speci\ufb01c hosts are trusted by Post\ufb01x to allow mail to be sent through the mail server to any destination based on this trust. When the mynetworks parameter has been set, you can then use the variable to explicitly tell Post\ufb01x the networks that your installation trusts.<\/p>\n

Figure shows an example setup for your always-connected corporate mail server. You can see where the mynetworks parameter comes into use. By default, the mynetworks parameter contains your localhost network (127.0.0.0\/8) and your network connections that have been con\ufb01gured in your system.
\nIn this example, you can see the Post\ufb01x server in the DMZ (demilitarized zone) on an IP address of 192.168.0.4\/24. Your internal network is in the subnet of 10.0.0.0\/24. Given Post\ufb01x\u2019s default mynetworks parameter, the 10.0.0.0\/24 network will not be allowed to relay mail through Post\ufb01x because it is not part of the Post\ufb01x server\u2019s network. To remedy this, you need to add the 10.0.0.0\/24\u00a0network to the mynetworks clause:
\nmynetworks = 127.0.0.0\/8, 192.168.0.0\/24, 10.0.0.0\/24<\/p>\n

\"\"
\nThis entry now allows relaying from localhost, the DMZ network, and also your internal network.
\nWhen mynetworks has been con\ufb01gured, the parameter smtpd_recipient_restrictions actually allows the relaying to take place. As you can see from the default main.cf con\ufb01guration we talked about before, this parameter has two objectives:
\n\u25a0 To allow all relays from machines that are in mynetworks<\/p>\n

\u25a0 To deny all other relays using the reject_unauth_destination(reject all unauthorized connections) clause<\/p>\n

Post\ufb01x also allows relaying to any domains listed in relay_domains. This parameter, by default, contains whatever is in the $mydomain parameter, which by default is your machine\u2019s con\ufb01gured domain. If you use the default setting, any untrusted sender (not in mynetworks) can relay mail through Post\ufb01x to any user at $mydomain. It should be obvious why this is the default, as this would mean that Post\ufb01x would accept mail for the domain it is hosting.<\/p>\n","protected":false},"excerpt":{"rendered":"

Post\ufb01x\u2019s relaying policy (allowing users to send mail through the mail server) is dictated by default via the mynetworks parameter. The mynetworks parameter tells Post\ufb01x what networks or speci\ufb01c hosts are trusted by Post\ufb01x to allow mail to be sent through the mail server to any destination based on this<\/p>\n","protected":false},"author":3,"featured_media":985,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[5],"tags":[],"class_list":["post-981","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-knowledgebase"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"https:\/\/i0.wp.com\/www.virtono.com\/community\/wp-content\/uploads\/2017\/06\/postfix1.gif?fit=300%2C300&ssl=1","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p7ISfL-fP","jetpack_likes_enabled":true,"jetpack-related-posts":[{"id":3492,"url":"https:\/\/www.virtono.com\/community\/tutorial-how-to\/how-to-install-and-configure-mail-server-on-ubuntu\/","url_meta":{"origin":981,"position":0},"title":"How to Install and Configure Mail Server on Ubuntu","author":"George B.","date":"June 11, 2023","format":false,"excerpt":"Setting up a mail server on Ubuntu can be a daunting task for many, but with the right guidance and understanding, it becomes an achievable goal. In this article, we will provide a step-by-step guide on how to install and configure a mail server on Ubuntu. 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