Properly support FreeBSD

We now disable all sendmail services and periodic services on FreeBSD
before attempting to start postfix. Additionally, this updates
mailer.conf mappings to use postfix applications rather than sendmail.

recipes/_common.rb

@@ -69,6 +69,47 @@ when 'omnios'
     command "svccfg import #{manifest_path}"
     notifies :restart, 'service[postfix]'
   end
+when 'freebsd'
+  # Actions are based on docs provided by FreeBSD:
+  # https://www.freebsd.org/doc/handbook/mail-changingmta.html
+  service 'sendmail' do
+    action :nothing
+  end
+
+  template '/etc/mail/mailer.conf' do
+    source 'mailer.erb'
+    owner 'root'
+    group 0
+    notifies :restart, 'service[postfix]'
+  end
+
+  execute 'switch_mailer_to_postfix' do
+    command [
+      'sysrc',
+      'sendmail_enable=NO',
+      'sendmail_submit_enable=NO',
+      'sendmail_outbound_enable=NO',
+      'sendmail_msp_queue_enable=NO',
+      'postfix_enable=YES',
+    ]
+    notifies :stop, 'service[sendmail]', :immediately
+    notifies :disable, 'service[sendmail]', :immediately
+    notifies :start, 'service[postfix]', :delayed
+    only_if "sysrc sendmail_enable sendmail_submit_enable sendmail_outbound_enable sendmail_msp_queue_enable | egrep -q '(YES|unknown variable)' || sysrc postfix_enable | egrep -q '(NO|unknown variable)'"
+  end
+
+  execute 'disable_periodic' do
+    # rubocop:disable Lint/ParenthesesAsGroupedExpression
+    environment ({ 'RC_CONFS' => '/etc/periodic.conf' })
+    command [
+      'sysrc',
+      'daily_clean_hoststat_enable=NO',
+      'daily_status_mail_rejects_enable=NO',
+      'daily_status_include_submit_mailq=NO',
+      'daily_submit_queuerun=NO',
+    ]
+    only_if "RC_CONFS=/etc/periodic.conf sysrc daily_clean_hoststat_enable daily_status_mail_rejects_enable daily_status_include_submit_mailq daily_submit_queuerun | egrep -q '(YES|unknown variable)'"
+  end
 end
 
 execute 'update-postfix-sender_canonical' do