Outbound spam can be extremely damaging to the ability of your system to successfully deliver mail so it is pragmatic to avoid delivering spam. Unlike inbound spam, outbound spam outbreaks require incident response (e.g. changing passwords of affected accounts). If the spam outbreak was identified by automated content scanning human verification could be helpful - but may be in violation of applicable privacy laws or company policies. Please consult your legal counsel & company stakeholders to determine policies regarding handling of suspected outbound spam that are suitable for your purposes. How such mail should ultimately be handled is beyond the scope of this document (though it may eventually be extended to provide some example recipes).
Rspamd tries to be suitable for outbound scanning with no or little configuration. With proper integration Rspamd should have knowledge of whether mail was sent by an authenticated user (and which) as well as the IP address the mail was received from. If mail was received from an authenticated user or an IP address listed in local_addrs several checks are immutably disabled:
check_local is set to trueuser ratelimit is applied (to authenticated users - does not deal with local_addrs)exclude_users and exclude_local settings (all save for RAMBLER_EMAILBL)Additionally, it is possible to disable/enable checks selectively and/or rescore checks for your authenticated users or relay IPs using settings module.
You might want to add non_smtpd_milters setting to point Rspamd proxy worker for scanning of the emails that are sent directly via sendmail or other local delivery agent. Here is an example for Postfix MTA:
# postfix/main.cf
smtpd_milters=inet:127.0.0.1:11332 # For inbound scan or outbound scan via SMTP
non_smtpd_milters=inet:127.0.0.1:11332 # For invocation via LDA
Here is an example configuration suitable for filtering outbound email.
# Global options
spamd_address = 127.0.0.1 11333 variant=rspamd
acl_smtp_data = acl_check_data
begin acl
acl_check_data:
# Set default value for a variable
warn
set acl_m_outspam = 0
# Always scan mail
warn
spam = nobody:true
# Honor "reject" action for inbound mail...
deny
! authenticated = *
condition = ${if eq{$spam_action}{reject}}
message = Discarded high-probability spam
# If it's our user set acl_m_outspam = 1 instead
warn
authenticated = *
condition = ${if eq{$spam_action}{reject}}
set acl_m_outspam = 1
accept
begin routers
# Apply special handling to messages with $acl_m_outspam==1
redirect_outbound_spam:
driver = redirect
condition = ${if eq{$acl_m_outspam}{1}}
data = admin@example.com
# <rest of configuration>
See the Exim specification for more information.
To enable scanning of outbound mail set the following in config/rspamd.ini:
[check]
authenticated=true
If you wish to honor reject action for authenticated users set the following:
[reject]
authenticated=true