tests: add "from" and "to" headers to the test email

Author: zuazo

test/kitchen/cookbooks/postfix-dovecot_test/files/default/tests/minitest/support/helpers.rb

@@ -9,6 +9,8 @@ module PostfixDovecotTest
     def send_test_mail(from, to)
 
       msgstr = <<-EOM
+From: #{from}
+To: #{to}
 Subject: Some cool subject for testing
 
 A blackhole email body.