30885bcc8a
Port 25 now is aligned with Mozilla's "Old" recommendations at https://ssl-config.mozilla.org/#server=postfix&server-version=3.3.0&config=old&openssl-version=1.1.1. See #1705
271 lines
15 KiB
Bash
Executable file
271 lines
15 KiB
Bash
Executable file
#!/bin/bash
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#
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# Postfix (SMTP)
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# --------------
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#
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# Postfix handles the transmission of email between servers
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# using the SMTP protocol. It is a Mail Transfer Agent (MTA).
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#
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# Postfix listens on port 25 (SMTP) for incoming mail from
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# other servers on the Internet. It is responsible for very
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# basic email filtering such as by IP address and greylisting,
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# it checks that the destination address is valid, rewrites
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# destinations according to aliases, and passses email on to
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# another service for local mail delivery.
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#
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# The first hop in local mail delivery is to Spamassassin via
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# LMTP. Spamassassin then passes mail over to Dovecot for
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# storage in the user's mailbox.
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#
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# Postfix also listens on port 587 (SMTP+STARTLS) for
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# connections from users who can authenticate and then sends
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# their email out to the outside world. Postfix queries Dovecot
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# to authenticate users.
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#
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# Address validation, alias rewriting, and user authentication
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# is configured in a separate setup script mail-users.sh
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# because of the overlap of this part with the Dovecot
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# configuration.
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source setup/functions.sh # load our functions
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source /etc/mailinabox.conf # load global vars
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# ### Install packages.
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# Install postfix's packages.
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#
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# * `postfix`: The SMTP server.
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# * `postfix-pcre`: Enables header filtering.
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# * `postgrey`: A mail policy service that soft-rejects mail the first time
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# it is received. Spammers don't usually try agian. Legitimate mail
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# always will.
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# * `ca-certificates`: A trust store used to squelch postfix warnings about
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# untrusted opportunistically-encrypted connections.
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echo "Installing Postfix (SMTP server)..."
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apt_install postfix postfix-sqlite postfix-pcre postgrey ca-certificates
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# ### Basic Settings
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# Set some basic settings...
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#
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# * Have postfix listen on all network interfaces.
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# * Make outgoing connections on a particular interface (if multihomed) so that SPF passes on the receiving side.
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# * Set our name (the Debian default seems to be "localhost" but make it our hostname).
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# * Set the name of the local machine to localhost, which means xxx@localhost is delivered locally, although we don't use it.
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# * Set the SMTP banner (which must have the hostname first, then anything).
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tools/editconf.py /etc/postfix/main.cf \
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inet_interfaces=all \
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smtp_bind_address=$PRIVATE_IP \
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smtp_bind_address6=$PRIVATE_IPV6 \
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myhostname=$PRIMARY_HOSTNAME\
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smtpd_banner="\$myhostname ESMTP Hi, I'm a Mail-in-a-Box (Ubuntu/Postfix; see https://mailinabox.email/)" \
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mydestination=localhost
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# Tweak some queue settings:
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# * Inform users when their e-mail delivery is delayed more than 3 hours (default is not to warn).
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# * Stop trying to send an undeliverable e-mail after 2 days (instead of 5), and for bounce messages just try for 1 day.
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tools/editconf.py /etc/postfix/main.cf \
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delay_warning_time=3h \
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maximal_queue_lifetime=2d \
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bounce_queue_lifetime=1d
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# ### Outgoing Mail
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# Enable the 'submission' port 587 smtpd server and tweak its settings.
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#
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# * Enable authentication. It's disabled globally so that it is disabled on port 25,
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# so we need to explicitly enable it here.
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# * Do not add the OpenDMAC Authentication-Results header. That should only be added
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# on incoming mail. Omit the OpenDMARC milter by re-setting smtpd_milters to the
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# OpenDKIM milter only. See dkim.sh.
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# * Even though we dont allow auth over non-TLS connections (smtpd_tls_auth_only below, and without auth the client cant
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# send outbound mail), don't allow non-TLS mail submission on this port anyway to prevent accidental misconfiguration.
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# Setting smtpd_tls_security_level=encrypt also triggers the use of the 'mandatory' settings below.
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# * Give it a different name in syslog to distinguish it from the port 25 smtpd server.
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# * Add a new cleanup service specific to the submission service ('authclean')
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# that filters out privacy-sensitive headers on mail being sent out by
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# authenticated users. By default Postfix also applies this to attached
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# emails but we turn this off by setting nested_header_checks empty.
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tools/editconf.py /etc/postfix/master.cf -s -w \
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"submission=inet n - - - - smtpd
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-o smtpd_sasl_auth_enable=yes
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-o syslog_name=postfix/submission
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-o smtpd_milters=inet:127.0.0.1:8891
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-o smtpd_tls_security_level=encrypt
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-o cleanup_service_name=authclean" \
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"authclean=unix n - - - 0 cleanup
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-o header_checks=pcre:/etc/postfix/outgoing_mail_header_filters
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-o nested_header_checks="
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# Install the `outgoing_mail_header_filters` file required by the new 'authclean' service.
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cp conf/postfix_outgoing_mail_header_filters /etc/postfix/outgoing_mail_header_filters
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# Modify the `outgoing_mail_header_filters` file to use the local machine name and ip
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# on the first received header line. This may help reduce the spam score of email by
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# removing the 127.0.0.1 reference.
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sed -i "s/PRIMARY_HOSTNAME/$PRIMARY_HOSTNAME/" /etc/postfix/outgoing_mail_header_filters
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sed -i "s/PUBLIC_IP/$PUBLIC_IP/" /etc/postfix/outgoing_mail_header_filters
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# Enable TLS on incoming connections. It is not required on port 25, allowing for opportunistic
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# encryption. On port 587 it is mandatory (see above). Shared and non-shared settings are
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# given here. Shared settings include:
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# * Require TLS before a user is allowed to authenticate.
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# * Set the path to the server TLS certificate and 2048-bit DH parameters for old DH ciphers.
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# For port 25 only:
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# * Disable extremely old versions of TLS and extremely unsafe ciphers, but some mail servers out in
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# the world are very far behind and if we disable too much, they may not be able to use TLS and
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# won't fall back to cleartext. So we don't disable too much. smtpd_tls_exclude_ciphers applies to
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# both port 25 and port 587, but because we override the cipher list for both, it probably isn't used.
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# Use Mozilla's "Old" recommendations at https://ssl-config.mozilla.org/#server=postfix&server-version=3.3.0&config=old&openssl-version=1.1.1
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# For port 587 (via the 'mandatory' settings):
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# * Use Mozilla's "Intermediate" TLS recommendations from https://ssl-config.mozilla.org/#server=postfix&server-version=3.3.0&config=intermediate&openssl-version=1.1.1
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# using and overriding the "high" cipher list so we don't conflict with the more permissive settings for port 25.
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tools/editconf.py /etc/postfix/main.cf \
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smtpd_tls_security_level=may\
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smtpd_tls_auth_only=yes \
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smtpd_tls_cert_file=$STORAGE_ROOT/ssl/ssl_certificate.pem \
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smtpd_tls_key_file=$STORAGE_ROOT/ssl/ssl_private_key.pem \
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smtpd_tls_dh1024_param_file=$STORAGE_ROOT/ssl/dh2048.pem \
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smtpd_tls_protocols="!SSLv2,!SSLv3" \
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smtpd_tls_ciphers=medium \
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tls_medium_cipherlist=ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:DHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA:ECDHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES256-SHA256:AES128-GCM-SHA256:AES256-GCM-SHA384:AES128-SHA256:AES256-SHA256:AES128-SHA:AES256-SHA:DES-CBC3-SHA \
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smtpd_tls_exclude_ciphers=aNULL,RC4 \
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smtpd_tls_mandatory_protocols="!SSLv2,!SSLv3,!TLSv1,!TLSv1.1" \
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smtpd_tls_mandatory_ciphers=high \
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tls_high_cipherlist=ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384 \
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smtpd_tls_mandatory_exclude_ciphers=aNULL,DES,3DES,MD5,DES+MD5,RC4 \
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tls_preempt_cipherlist=no \
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smtpd_tls_received_header=yes
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# Prevent non-authenticated users from sending mail that requires being
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# relayed elsewhere. We don't want to be an "open relay". On outbound
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# mail, require one of:
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#
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# * `permit_sasl_authenticated`: Authenticated users (i.e. on port 587).
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# * `permit_mynetworks`: Mail that originates locally.
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# * `reject_unauth_destination`: No one else. (Permits mail whose destination is local and rejects other mail.)
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tools/editconf.py /etc/postfix/main.cf \
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smtpd_relay_restrictions=permit_sasl_authenticated,permit_mynetworks,reject_unauth_destination
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# ### DANE
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# When connecting to remote SMTP servers, prefer TLS and use DANE if available.
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#
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# Prefering ("opportunistic") TLS means Postfix will use TLS if the remote end
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# offers it, otherwise it will transmit the message in the clear. Postfix will
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# accept whatever SSL certificate the remote end provides. Opportunistic TLS
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# protects against passive easvesdropping (but not man-in-the-middle attacks).
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# Since we'd rather have poor encryption than none at all, we use Mozilla's
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# "Old" recommendations at https://ssl-config.mozilla.org/#server=postfix&server-version=3.3.0&config=old&openssl-version=1.1.1
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# for opportunistic encryption but "Intermediate" recommendations when DANE
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# is used (see next and above). The cipher lists are set above.
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# DANE takes this a step further:
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# Postfix queries DNS for the TLSA record on the destination MX host. If no TLSA records are found,
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# then opportunistic TLS is used. Otherwise the server certificate must match the TLSA records
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# or else the mail bounces. TLSA also requires DNSSEC on the MX host. Postfix doesn't do DNSSEC
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# itself but assumes the system's nameserver does and reports DNSSEC status. Thus this also
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# relies on our local DNS server (see system.sh) and `smtp_dns_support_level=dnssec`.
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#
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# The `smtp_tls_CAfile` is superflous, but it eliminates warnings in the logs about untrusted certs,
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# which we don't care about seeing because Postfix is doing opportunistic TLS anyway. Better to encrypt,
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# even if we don't know if it's to the right party, than to not encrypt at all. Instead we'll
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# now see notices about trusted certs. The CA file is provided by the package `ca-certificates`.
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tools/editconf.py /etc/postfix/main.cf \
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smtp_tls_protocols=\!SSLv2,\!SSLv3 \
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smtp_tls_ciphers=medium \
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smtp_tls_exclude_ciphers=aNULL,RC4 \
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smtp_tls_security_level=dane \
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smtp_dns_support_level=dnssec \
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smtp_tls_mandatory_protocols="!SSLv2,!SSLv3,!TLSv1,!TLSv1.1" \
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smtp_tls_mandatory_ciphers=high \
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smtp_tls_CAfile=/etc/ssl/certs/ca-certificates.crt \
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smtp_tls_loglevel=2
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# ### Incoming Mail
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# Pass any incoming mail over to a local delivery agent. Spamassassin
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# will act as the LDA agent at first. It is listening on port 10025
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# with LMTP. Spamassassin will pass the mail over to Dovecot after.
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#
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# In a basic setup we would pass mail directly to Dovecot by setting
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# virtual_transport to `lmtp:unix:private/dovecot-lmtp`.
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tools/editconf.py /etc/postfix/main.cf virtual_transport=lmtp:[127.0.0.1]:10025
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# Because of a spampd bug, limit the number of recipients in each connection.
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# See https://github.com/mail-in-a-box/mailinabox/issues/1523.
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tools/editconf.py /etc/postfix/main.cf lmtp_destination_recipient_limit=1
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# Who can send mail to us? Some basic filters.
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#
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# * `reject_non_fqdn_sender`: Reject not-nice-looking return paths.
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# * `reject_unknown_sender_domain`: Reject return paths with invalid domains.
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# * `reject_authenticated_sender_login_mismatch`: Reject if mail FROM address does not match the client SASL login
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# * `reject_rhsbl_sender`: Reject return paths that use blacklisted domains.
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# * `permit_sasl_authenticated`: Authenticated users (i.e. on port 587) can skip further checks.
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# * `permit_mynetworks`: Mail that originates locally can skip further checks.
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# * `reject_rbl_client`: Reject connections from IP addresses blacklisted in zen.spamhaus.org
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# * `reject_unlisted_recipient`: Although Postfix will reject mail to unknown recipients, it's nicer to reject such mail ahead of greylisting rather than after.
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# * `check_policy_service`: Apply greylisting using postgrey.
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#
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# Notes: #NODOC
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# permit_dnswl_client can pass through mail from whitelisted IP addresses, which would be good to put before greylisting #NODOC
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# so these IPs get mail delivered quickly. But when an IP is not listed in the permit_dnswl_client list (i.e. it is not #NODOC
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# whitelisted) then postfix does a DEFER_IF_REJECT, which results in all "unknown user" sorts of messages turning into #NODOC
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# "450 4.7.1 Client host rejected: Service unavailable". This is a retry code, so the mail doesn't properly bounce. #NODOC
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tools/editconf.py /etc/postfix/main.cf \
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smtpd_sender_restrictions="reject_non_fqdn_sender,reject_unknown_sender_domain,reject_authenticated_sender_login_mismatch,reject_rhsbl_sender dbl.spamhaus.org" \
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smtpd_recipient_restrictions=permit_sasl_authenticated,permit_mynetworks,"reject_rbl_client zen.spamhaus.org",reject_unlisted_recipient,"check_policy_service inet:127.0.0.1:10023"
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# Postfix connects to Postgrey on the 127.0.0.1 interface specifically. Ensure that
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# Postgrey listens on the same interface (and not IPv6, for instance).
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# A lot of legit mail servers try to resend before 300 seconds.
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# As a matter of fact RFC is not strict about retry timer so postfix and
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# other MTA have their own intervals. To fix the problem of receiving
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# e-mails really latter, delay of greylisting has been set to
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# 180 seconds (default is 300 seconds).
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tools/editconf.py /etc/default/postgrey \
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POSTGREY_OPTS=\"'--inet=127.0.0.1:10023 --delay=180'\"
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# We are going to setup a newer whitelist for postgrey, the version included in the distribution is old
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cat > /etc/cron.daily/mailinabox-postgrey-whitelist << EOF;
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#!/bin/bash
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# Mail-in-a-Box
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# check we have a postgrey_whitelist_clients file and that it is not older than 28 days
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if [ ! -f /etc/postgrey/whitelist_clients ] || find /etc/postgrey/whitelist_clients -mtime +28 | grep -q '.' ; then
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# ok we need to update the file, so lets try to fetch it
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if curl https://postgrey.schweikert.ch/pub/postgrey_whitelist_clients --output /tmp/postgrey_whitelist_clients -sS --fail > /dev/null 2>&1 ; then
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# if fetching hasn't failed yet then check it is a plain text file
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# curl manual states that --fail sometimes still produces output
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# this final check will at least check the output is not html
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# before moving it into place
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if [ "\$(file -b --mime-type /tmp/postgrey_whitelist_clients)" == "text/plain" ]; then
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mv /tmp/postgrey_whitelist_clients /etc/postgrey/whitelist_clients
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service postgrey restart
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else
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rm /tmp/postgrey_whitelist_clients
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fi
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fi
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fi
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EOF
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chmod +x /etc/cron.daily/mailinabox-postgrey-whitelist
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/etc/cron.daily/mailinabox-postgrey-whitelist
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# Increase the message size limit from 10MB to 128MB.
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# The same limit is specified in nginx.conf for mail submitted via webmail and Z-Push.
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tools/editconf.py /etc/postfix/main.cf \
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message_size_limit=134217728
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# Allow the two SMTP ports in the firewall.
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ufw_allow smtp
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ufw_allow submission
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# Restart services
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restart_service postfix
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restart_service postgrey
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