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414 lines
13 KiB
Markdown
414 lines
13 KiB
Markdown
# Gmail Apple II Email Gateway
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## Motivation
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To connect an Apple IIGS to Gmail, allowing messages to be sent and received.
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I used Ewen Wannop (aka Speccie)'s SAM2 email client, running under GSOS 6.0.4.
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This should also work with GSOS 6.0.1.
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Speccie's website is [here](https://speccie.uk/software/)
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In order to communicate on today's Internet Transport Layer Security (TLS)
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is necessary. Retro machines such as the Apple II series lack the processor
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power to perform the necessary encryption, so it is necessary to have a proxy
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system in between the Apple II and Gmail's servers. This proxy machine can
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'speak' in today's encrypted TLS protocols to Gmail, and in plaintext to our
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Apple II. I chose to use a Raspberry Pi 4 (2GB version) running the Raspbian
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Linux operating system version 10.
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## Prerequisites
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- An Apple IIgs. Mine is a ROM01.
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- Enough memory I have a 4MB RAM card.
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- Enough disk space. I have a MicroDrive/Turbo with 32MB volumes.
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- A compatible ethernet card. I used an Uthernet II.
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- GSOS 6.0.1 or 6.0.4 installed.
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- Marinetti 3.0 installed. I used 3.0b11.
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- A Raspberry Pi running Raspbian 10
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I don't cover any of the above in this README. You can find information
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[elsewhere](http://www.apple2.org/marinetti/) on how to set up Marinetti.
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## Software Used
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I use three separate packages on the Raspberry Pi, as follows:
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- *Postfix* This is a full-featured mail tranfer agent. We will use it
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to send mail to the Gmail servers over the SMTPS port with TLS, and to
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act as a plaintext SMTP server for the local network.
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- *Fetchmail* Fetchmail is configured to pull down messages from a Gmail
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inbox and store it on the Raspberry Pi in `/var/mail/` using the IMAP
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protocol with TLS.
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- *Dovecot* Dovecot provides a POP3 server to the local network, serving
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the files in `/var/mail`.
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## Principle of Operation
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### Incoming Messages
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- Message is sent to Gmail username@gmail.com
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- Fetchmail runs as a service on the Pi and monitors Gmail using IMAP
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IDLE. As soon as a message shows up in the INBOX it downloads it
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and places it in `/var/mail/pi` (for username `pi`). Fetchmail leaves
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the email on the Gmail server (this can be changed if desired.)
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- SAM2 mail client on the Apple IIgs is configured to use the IP
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of the Raspberry Pi as its POP3 email server. When it asks for new
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messages, Dovecot will serve the request on port 110. When messages are
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downloaded using POP3, they are deleted from `/var/mail/pi` on the
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Raspberry Pi.
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### Outgoing Messages
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- The SAM2 mail client on the Apple IIgs is configured to use the IP of the
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Raspberry Pi as its SMTP server. Outgoing emails are sent to port 25
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on the Raspberry Pi.
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- Postfix handles the plaintext SMTP dialog with SAM2 mail and relays the
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message to Gmail's servers using SMTPS with TLS.
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## Installing the Packages on Rasbian
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Install the packages with root privs on the Pi:
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```
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sudo apt update
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sudo apt upgrade
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sudo apt install postfix postfix-pcre
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sudo apt install dovecot-common dovecot-pop3d
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sudo apt install fetchmail
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```
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## Obtaining App Passwords from Google
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Google provides a mechanism to allow non-Google apps to connect to Gmail
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called *App Passwords*.
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Google's help page is [here](https://support.google.com/accounts/answer/185833?hl=en)
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In order to use the App Passwords method of authentication 2-Step Verification
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must be turned on for the account. This is the general approach:
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- In a web browser log in to the Gmail account and go to
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[Google Account](https://myaccount.google.com/).
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- In the panel on the left, choose *Security*.
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- Enable *2-Step Verification* for the account.
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- The option *App Passwords* will now appear. Select this option.
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- At the bottom, choose *Select app* and enter a descriptive name for
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the app.
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- Choose *Select Device* and choose the device.
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- Click *Generate*.
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- A 16 character App Password will be shown on the screen. Write this value
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down because you will need it later in the configuration.
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I generated two separate App Passwords - one for SMTPS and one for IMAPS.
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## Configuring the Packages
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### Postfix
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The Postfix MTA configuration files are in `/etc/postfix`. Of the three
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packages, Postfix is the most complex to configure and has many available
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options.
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[This](https://www.linode.com/docs/email/postfix/postfix-smtp-debian7/)
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page was helpful for configuring Postfix.
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Be aware that this configuration amounts to an open relay from unsecured
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SMTP to SMTPS, and must never be place on the public internet, or it will be
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abused by spammers! Keep it on your private LAN segment only!
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We will modify a number of configuration files:
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- `/etc/postfix/command_filter`
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- `/etc/postfix/main.cf`
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- `/etc/postfix/master.cf`
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- `/etc/postfix/sasl/sasl_passwd`
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- `/etc/postfix/sasl/sasl_passwd.db`
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Once Dovecot has been configured, the service may be controlled as follows:
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- `systemctl start postfix` - start service.
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- `systemctl stop postfix` - stop service.
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- `systemctl status postfix` - status of service.
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#### `command_filter`
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For some reason, SAM2 sends a bunch of mail headers *after* the email message
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has been tranmitted to Postfix's SMTP server. Postfix gets very unhappy about
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this. The solution is to filter them out using Postfix's
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`smtpd_command_filter` function.
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The `command_filter` files contains the regular expressions to filter out these
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unwanted headers:
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```
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/^Message-ID:.*$/ NOOP
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/^MIME-version:.*$/ NOOP
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/^Content-Type:.*$/ NOOP
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/^Content-transfer-encoding:.*$/ NOOP
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/^From:.*$/ NOOP
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/^To:.*$/ NOOP
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/^In-Reply-To:.*$/ NOOP
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/^Subject:.*$/ NOOP
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/^Date:.*$/ NOOP
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/^X-Mailer:.*$/ NOOP
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```
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#### `main.cf`
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This is the main Postfix configuration file.
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I adjusted `smtpd_use_tls = no` to turn off TLS for the SMTP service offered to
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the Apple II and added `smtpd_command_filter =
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pcre:/etc/postfix/command_filter` to activate the filter discussed above.
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`relayhost = [smtp.gmail.com]:587` will forward email to Gmail's SMTPS server.
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I adjusted `smtpd_relay_restrictions = permit_mynetworks
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permit_sasl_authenticated defer_unauth_destination` to allow network hosts
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listed in `mynetworks` to relay messages to the `relayhost`.
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My home network is 192.168.10.0/24, so I added it here:
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`mynetworks = 192.168.10.0/24 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128`.
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You should adjust this line to match your own LAN subnet.
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Finally I added the following block of settings to enabled SASL authentication
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when talking to Gmail:
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```
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# Enable SASL authentication
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smtp_sasl_auth_enable = yes
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# Disallow methods that allow anonymous authentication
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smtp_sasl_security_options = noanonymous
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# Location of sasl_passwd
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smtp_sasl_password_maps = hash:/etc/postfix/sasl/sasl_passwd
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# Enable STARTTLS encryption
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smtp_tls_security_level = encrypt
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# Location of CA certificates
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smtp_tls_CAfile = /etc/ssl/certs/ca-certificates.crt
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```
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The whole thing looks like this:
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```
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# See /usr/share/postfix/main.cf.dist for a commented, more complete version
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# Debian specific: Specifying a file name will cause the first
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# line of that file to be used as the name. The Debian default
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# is /etc/mailname.
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#myorigin = /etc/mailname
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smtpd_banner = $myhostname ESMTP $mail_name (Raspbian)
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biff = no
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# appending .domain is the MUA's job.
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append_dot_mydomain = no
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# Uncomment the next line to generate "delayed mail" warnings
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#delay_warning_time = 4h
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readme_directory = no
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# See http://www.postfix.org/COMPATIBILITY_README.html -- default to 2 on
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# fresh installs.
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compatibility_level = 2
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# TLS parameters
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smtpd_tls_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem
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smtpd_tls_key_file=/etc/ssl/private/ssl-cert-snakeoil.key
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smtpd_use_tls=no
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smtpd_tls_session_cache_database = btree:${data_directory}/smtpd_scache
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smtp_tls_session_cache_database = btree:${data_directory}/smtp_scache
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# See /usr/share/doc/postfix/TLS_README.gz in the postfix-doc package for
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# information on enabling SSL in the smtp client.
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relayhost = [smtp.gmail.com]:587
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smtpd_command_filter = pcre:/etc/postfix/command_filter
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smtpd_relay_restrictions = permit_mynetworks permit_sasl_authenticated defer_unauth_destination
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#smtpd_recipient_restrictions = permit_mynetworks
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myhostname = raspberrypi.home
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alias_maps = hash:/etc/aliases
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alias_database = hash:/etc/aliases
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mydestination = $myhostname, raspberrypi, localhost.localdomain, , localhost
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mynetworks = 192.168.10.0/24 127.0.0.0/8 [::ffff:127.0.0.0]/104 [::1]/128
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mailbox_size_limit = 0
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recipient_delimiter = +
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inet_interfaces = all
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inet_protocols = all
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# Enable SASL authentication
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smtp_sasl_auth_enable = yes
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# Disallow methods that allow anonymous authentication
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smtp_sasl_security_options = noanonymous
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# Location of sasl_passwd
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smtp_sasl_password_maps = hash:/etc/postfix/sasl/sasl_passwd
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# Enable STARTTLS encryption
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smtp_tls_security_level = encrypt
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# Location of CA certificates
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smtp_tls_CAfile = /etc/ssl/certs/ca-certificates.crt
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```
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#### `master.cf`
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`master.cf` does not need to be modified other than to enable `smtpd` by
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uncommenting the following line:
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```
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# ==========================================================================
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# service type private unpriv chroot wakeup maxproc command + args
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# (yes) (yes) (no) (never) (100)
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# ==========================================================================
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smtp inet n - y - - smtpd
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```
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If you require verbose debugging information to get the SMTP connection
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working, change the line as follows:
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```
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smtp inet n - y - - smtpd y
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```
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#### `sasl/sasl_passwd` and `sasl/sasl_passwd.db`
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Create the directory `/etc/postfix/sasl`.
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Create the file `/etc/postfix/sasl_passwd` as follows:
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```
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[smtp.gmail.com]:587 username@gmail.com:xxxx xxxx xxxx xxxx
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```
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where `username` is your Gmail account name and `xxxx xxxx xxxx xxxx` is the
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App Password Google gave you.
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Run: `sudo postmap /etc/postfix/sasl_passwd` to build the hash file
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`sasl_passwd.db`.
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### Dovecot
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The Dovecot POP3 server configuration files are in `/etc/dovecot`. I had
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to edit the following two files (starting from the default Raspbian package):
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- `/etc/dovecot/conf.d/10-auth.conf`
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- `/etc/dovecot/conf.d/10-master.conf`
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Once Dovecot has been configured, the service may be controlled as follows:
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- `systemctl start dovecot` - start service.
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- `systemctl stop dovecot` - stop service.
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- `systemctl status dovecot` - status of service.
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#### `10-auth.conf`
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The only non-comment lines are as follows:
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```
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disable_plaintext_auth = no
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auth_mechanisms = plain
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!include auth-system.conf.ext
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```
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#### `10-master.conf`
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I enabled the POP3 service on port 110 by uncommenting the `port = 110`
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line as follows:
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```
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service pop3-login {
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inet_listener pop3 {
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port = 110
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}
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inet_listener pop3s {
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#port = 995
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#ssl = yes
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}
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}
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```
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### Fetchmail
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Fetchmail's configuration is in the file `/etc/fetchmail`. It should look
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like this:
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```
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set postmaster "pi"
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set bouncemail
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set no spambounce
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set softbounce
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set properties ""
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poll imap.gmail.com with proto IMAP auth password
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user 'username' is pi here
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password 'xxxx xxxx xxxx xxxx'
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ssl, sslcertck, idle
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```
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Replace the `xxxx xxxx xxxx xxxx` with the App Password Google gave you.
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Replace `username` with your email account name.
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Make sure the permissions on the configuration file are okay:
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```
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chmod 600 /etc/fetchmailrc
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chown fetchmail.root /etc/fetchmailrc
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```
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Edit `/etc/default/fetchmail` to enable the Fetchmail service:
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```
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START_DAEMON=yes
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```
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Service controls:
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- `systemctl start fetchmail` - start service.
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- `systemctl stop fetchmail` - stop service.
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- `systemctl status fetchmail` - status of service.
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## Testing
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Log messages from all these packages are written to `/var/log/mail.log`.
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You can test the Postfix SMTP server using `telnet`. Be aware that it may
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not work the same way from the Pi (ie: localhost) than from a different
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machine on your LAN, so it is better to connect from another host.
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Connect to SMTP like this `telnet raspberrypi 25`. Typing the following
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commands should send an email:
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```
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HELO myhost.mydomain.com
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MAIL FROM:<myaccount@mydomain.com>
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RCPT TO:<someotheraccount@somedomain.com>
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DATA
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Subject: Test message
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This is just
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a simple test.
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.
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```
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The final period on its own serves to terminate the message and signal to
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Postfix that it should process the DATA block and enqueue the message.
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## Configuring SAM2 Email Client on the GS
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Configuring the client is simple:
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- Incoming mail via POP3
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- Hostname: hostname or IP address of your Raspberry Pi
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- Port: Default (110)
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- Username and password: Your Raspberry Pi account credentials
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- Outgoing mail via SMTP
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- Hostname: hostname or IP address of your Raspberry Pi
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- Port: Default (25)
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- Username and password: Your Raspberry Pi account credentials
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Bobbi
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Jun 17, 2020
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*bobbi.8bit@gmail.com*
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