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335 lines
8.7 KiB
Markdown
335 lines
8.7 KiB
Markdown
Getting started with Postfix, an open source mail transfer agent
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======
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[Postfix][1] is a great program that routes and delivers email to accounts that are external to the system. It is currently used by approximately [33% of internet mail servers][2]. In this article, I'll explain how you can use Postfix to send mail using Gmail with two-factor authentication enabled.
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Before you get Postfix up and running, however, you need to have some items lined up. Following are instructions on how to get it working on a number of distros.
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### Prerequisites
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* An installed OS (Ubuntu/Debian/Fedora/Centos/Arch/FreeBSD/OpenSUSE)
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* A Google account with two-factor authentication
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* A working internet connection
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### Step 1: Prepare Google
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Open a web browser and log into your Google account. Once you’re in, go to your settings by clicking your picture and selecting "Google Account.” Click “Sign-in & security” and scroll down to "App passwords.” Use your password to log in. Then you can create a new app password (I named mine "postfix Setup”).
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Note the crazy password (shown below), which I will use throughout this article.
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### Step 2: Install Postfix
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Before you can configure the mail client, you need to install it. You must also install either the `mailutils` or `mailx` utility, depending on the OS you're using. Here's how to install it for each OS:
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**Debian/Ubuntu** :
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```
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apt-get update && apt-get install postfix mailutils
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```
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**Fedora** :
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```
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dnf update && dnf install postfix mailx
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```
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**Centos** :
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```
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yum update && yum install postfix mailx cyrus-sasl cyrus-sasl-plain
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```
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**Arch** :
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```
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pacman -Sy postfix mailutils
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```
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**FreeBSD** :
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```
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portsnap fetch extract update
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cd /usr/ports/mail/postfix
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make config
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```
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In the configuration dialog, select "SASL support." All other options can remain the same.
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From there: `make install clean`
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Install `mailx` from the binary package: `pkg install mailx`
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**OpenSUSE** :
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```
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zypper update && zypper install postfix mailx cyrus-sasl
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```
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### Step 3: Set up Gmail authentication
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Once you've installed Postfix, you can set up Gmail authentication. Since you have created the app password, you need to put it in a configuration file and lock it down so no one else can see it. Fortunately, this is simple to do:
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**Ubuntu/Debian/Fedora/Centos/Arch/OpenSUSE** :
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```
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vim /etc/postfix/sasl_passwd
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```
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Add this line:
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```
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[smtp.gmail.com]:587 ben.heffron@gmail.com:thgcaypbpslnvgce
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```
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Save and close the file. Since your Gmail password is stored as plaintext, make the file accessible only by root to be extra safe.
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```
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chmod 600 /etc/postfix/sasl_passwd
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```
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**FreeBSD** :
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```
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vim /usr/local/etc/postfix/sasl_passwd
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```
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Add this line:
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```
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[smtp.gmail.com]:587 ben.heffron@gmail.com:thgcaypbpslnvgce
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```
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Save and close the file. Since your Gmail password is stored as plaintext, make the file accessible only by root to be extra safe.
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```
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chmod 600 /usr/local/etc/postfix/sasl_passwd
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```
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### Step 4: Get Postfix moving
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This step is the "meat and potatoes"—everything you've done so far has been preparation.
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Postfix gets its configuration from the `main.cf` file, so the settings in this file are critical. For Google, it is mandatory to enable the correct SSL settings.
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Here are the six options you need to enter or update on the `main.cf` to make it work with Gmail (from the [SASL readme][3]):
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* The **smtp_sasl_auth_enable** setting enables client-side authentication. We will configure the client’s username and password information in the second part of the example.
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* The **relayhost** setting forces the Postfix SMTP to send all remote messages to the specified mail server instead of trying to deliver them directly to their destination.
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* With the **smtp_sasl_password_maps** parameter, we configure the Postfix SMTP client to send username and password information to the mail gateway server.
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* Postfix SMTP client SASL security options are set using **smtp_sasl_security_options** , with a whole lot of options. In this case, it will be nothing; otherwise, Gmail won’t play nicely with Postfix.
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* The **smtp_tls_CAfile** is a file containing CA certificates of root CAs trusted to sign either remote SMTP server certificates or intermediate CA certificates.
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* From the [configure settings page:][4] **stmp_use_tls** uses TLS when a remote SMTP server announces STARTTLS support, the default is not using TLS.
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**Ubuntu/Debian/Arch**
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These three OSes keep their files (certificates and `main.cf`) in the same location, so this is all you need to put in there:
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```
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vim /etc/postfix/main.cf
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```
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If the following values aren’t there, add them:
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```
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relayhost = [smtp.gmail.com]:587
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smtp_use_tls = yes
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smtp_sasl_auth_enable = yes
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smtp_sasl_security_options =
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smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
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smtp_tls_CAfile = /etc/ssl/certs/ca-certificates.crt
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```
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Save and close the file.
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**Fedora/CentOS**
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These two OSes are based on the same underpinnings, so they share the same updates.
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```
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vim /etc/postfix/main.cf
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```
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If the following values aren’t there, add them:
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```
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relayhost = [smtp.gmail.com]:587
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smtp_use_tls = yes
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smtp_sasl_auth_enable = yes
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smtp_sasl_security_options =
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smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
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smtp_tls_CAfile = /etc/ssl/certs/ca-bundle.crt
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```
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Save and close the file.
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**OpenSUSE**
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```
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vim /etc/postfix/main.cf
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```
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If the following values aren’t there, add them:
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```
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relayhost = [smtp.gmail.com]:587
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smtp_use_tls = yes
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smtp_sasl_auth_enable = yes
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smtp_sasl_security_options =
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smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
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smtp_tls_CAfile = /etc/ssl/ca-bundle.pem
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```
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Save and close the file.
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OpenSUSE also requires that you modify the Postfix master process configuration file `master.cf`. Open it for editing:
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```
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vim /etc/postfix/master.cf
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```
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Uncomment the line that reads:
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```
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#tlsmgr unix - - n 1000? 1 tlsmg
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```
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It should look like this:
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```
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tlsmgr unix - - n 1000? 1 tlsmg
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```
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Save and close the file.
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**FreeBSD**
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```
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vim /usr/local/etc/postfix/main.cf
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```
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If the following values aren’t there, add them:
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```
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relayhost = [smtp.gmail.com]:587
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smtp_use_tls = yes
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smtp_sasl_auth_enable = yes
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smtp_sasl_security_options =
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smtp_sasl_password_maps = hash:/usr/local/etc/postfix/sasl_passwd
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smtp_tls_CAfile = /etc/mail/certs/cacert.pem
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```
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Save and close the file.
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### Step 5: Set up the password file
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Remember that password file you created? Now you need to feed it into Postfix using `postmap`. This is part of the `mailutils` or `mailx` utilities.
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**Debian, Ubuntu, Fedora, CentOS, OpenSUSE, Arch Linux**
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```
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postmap /etc/postfix/sasl_passwd
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```
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**FreeBSD**
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```
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postmap /usr/local/etc/postfix/sasl_passwd
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```
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### Step 6: Get Postfix grooving
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To get all the settings and configurations working, you must restart Postfix.
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**Debian, Ubuntu, Fedora, CentOS, OpenSUSE, Arch Linux**
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These guys make it simple to restart:
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```
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systemctl restart postfix.service
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```
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**FreeBSD**
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To start Postfix at startup, edit `/etc/rc.conf`:
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```
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vim /etc/rc.conf
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```
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Add the line:
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```
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postfix_enable=YES
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```
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Save and close the file. Then start Postfix by running:
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```
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service postfix start
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```
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### Step 7: Test it
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Now for the big finale—time to test it to see if it works. The `mail` command is another tool installed with `mailutils` or `mailx`.
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```
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echo Just testing my sendmail gmail relay" | mail -s "Sendmail gmail Relay" ben.heffron@gmail.com
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```
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This is what I used to test my settings, and then it came up in my Gmail.
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Now you can use Gmail with two-factor authentication in your Postfix setup.
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--------------------------------------------------------------------------------
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via: https://opensource.com/article/18/8/postfix-open-source-mail-transfer-agent
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作者：[Ben Heffron][a]
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选题：[lujun9972](https://github.com/lujun9972)
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译者：[译者ID](https://github.com/译者ID)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]:https://opensource.com/users/elheffe
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[1]:http://www.postfix.org/start.html
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[2]:http://www.securityspace.com/s_survey/data/man.201806/mxsurvey.html
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[3]:http://www.postfix.org/SASL_README.html
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[4]:http://www.postfix.org/postconf.5.html#smtp_tls_security_level
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