(i.e., authorize by IP address). Let's start with the steps to configure postfix with gmail smtp relay server. But now I want to be able to use the mailserver to send the occasional mail myself. Relay Host Configuration I’m running Postfix on Debian as an MX for a small LAN and trying to get SMTPS working with mobile.charter.net over port 587. Set up postfix in a way that it will relay the outgoing email through the actual ISP. I've setup a webserver with Postfix to receive mail for a whole bunch of (virtual) domains and that works perfectly. Users in the office/branch use this system to send mail internally. If you want to avoid an issue due to changing dynamic IP addresses, you'll want to setup SMTP authentication. Setup Postfix to Relay Mail for Specific Domains or Users. Postfix: Allow a certain sender only from a certain IP address. First, configure Postfix to act as a mail relay: The problem is that they have dynamic ip addresses and most mailservers will not accept incoming mail from a server on a dynamic ip address. Find the following line. Edit the Postfix main configuration file on server B. sudo nano /etc/postfix/main.cf. External mail is relayed to a central mail-server such as main office or ISP. Once Postfix SMTP server is installed on server B, let’s configure SMTP relay. Best practices are to allow relaying only when authentication passes. Since we are using firewalld we will add a rule using firewalld to allow smtp service # firewall-cmd --permanent --add-service=smtp . I'd be satisfied short-term with relaying all email from their IP and blocking everything from their address otherwise. I want to allow specific IP addresses to be open relay in Postfix.I know i need to add the following conf in /etc/postfix/main.cf mynetworks = 127.0.0.0/8, a.b.c.d/e, x.x.x.x/x But we want to send emails with accounts that doesn't not exist to the system. Postfix on Local Network as Relay Host. I have been working with my mail server a lot lately and I ran into some problems of getting mail delivered to Outlook.com Mail Accounts (Hotmail.com, Outlook.com, Live.com, etc) but I will discuss that more in another article (In Short two months later and still can’t). Install Packages. That will let e-mail clients relay mail, but only if they're originating either from the mail server, or any of the computers in the IP subnetwork 168.100.189.. Network configuration The final, and perhaps most important, configuration parameter for Postfix, is the inet_interfaces parameter. This does not open you up to be an open relay in case an IP address changes and now belongs to somebody else without you modifying your configuration accordingly. ssh sammy @ your_server_ip; Normally, the Postfix installation process uses some interactive screens to prompt you for information. May 30, 2016. If you want to relay via your own mail server, an alternative would be to update your mynetworks setting on the target mail server to accept e-mail without authentication (i.e., authorize by IP address). relayhost = By default, its value is not set. Postfix: Allow relaying for external IP address. Now, we want Postfix to authenticate with the SMTP server. I can't figure out how to set that up. I remember I once had a setup like this where there was a file I could simply add an IP or IP range and postfix would allow relay to only those IPs. So I tried adding their IP to mynetworks in postfix's main.cf. The solution is rather simple. I followed a few links off google for setting this up along with a post on serverfault with a similar question. Install postfix and other dependency packages for SASL authentication Postfix SMTP Relay via port 587. To prevent any possible errors during this setup, let’s preconfigure this information before we start the installation process. This configuration provides for the configuration where Postfix is running on an in-office server.