<commit_before>Forward Confirmed RDNS
================================

http://en.wikipedia.org/wiki/FCrDNS

DESCRIPTION
--------------------------
Determine if the SMTP sender has matching forward and reverse DNS.

Sets the connection note fcrdns.


CONFIGURATION
--------------------------
Edit config/connect.fcrdns.ini

You can also override the connection blocking settings with the rdns_access
plugin. Make sure it's enabled in config/plugins and listed *before* this
fcrdns plugin.


WHY IT WORKS
--------------------------
The reverse DNS of zombie PCs is out of the spam operators control. Their
only way to pass this test is to limit themselves to hosts with matching
forward and reverse DNS. This presents a significant hurdle.


HOW IT'S DONE
------------------
From WikiPedia: [Forward Confirmed Reverse DNS](http://en.wikipedia.org/wiki/FcRDNS)

1. First a reverse DNS lookup (PTR query) is performed on the IP address,
   which returns a list of zero or more PTR records.

2. For each domain name returned in the PTR query results, a regular
   'forward' DNS lookup (type A or AAAA query) is then performed.

3. Any A or AAAA record returned by the second query is then compared
   against the original IP address. If there is a match, FCrDNS passes.


iprev
--------------------------

[RFC 1912](http://www.ietf.org/rfc/rfc1912.txt)
[RFC 5451](http://www.ietf.org/rfc/rfc5451.txt)
[RFC 7001](http://tools.ietf.org/html/rfc7001#section-3)
<commit_msg>fcrdns: noted that iprev is saved to Auth-Res header<commit_after>Forward Confirmed RDNS
================================

http://en.wikipedia.org/wiki/FCrDNS

DESCRIPTION
--------------------------
Determine if the SMTP sender has matching forward and reverse DNS.

Sets the connection note fcrdns.


CONFIGURATION
--------------------------
Edit config/connect.fcrdns.ini

You can also override the connection blocking settings with the rdns_access
plugin. Make sure it's enabled in config/plugins and listed *before* this
fcrdns plugin.


WHY IT WORKS
--------------------------
The reverse DNS of zombie PCs is out of the spam operators control. Their
only way to pass this test is to limit themselves to hosts with matching
forward and reverse DNS. This presents a significant hurdle.


HOW IT'S DONE
------------------
From WikiPedia: [Forward Confirmed Reverse DNS](http://en.wikipedia.org/wiki/FcRDNS)

1. First a reverse DNS lookup (PTR query) is performed on the IP address,
   which returns a list of zero or more PTR records.

2. For each domain name returned in the PTR query results, a regular
   'forward' DNS lookup (type A or AAAA query) is then performed.

3. Any A or AAAA record returned by the second query is then compared
   against the original IP address. If there is a match, FCrDNS passes.


iprev
--------------------------
The iprev results are added to the Authentication-Results header.

[RFC 1912](http://www.ietf.org/rfc/rfc1912.txt)
[RFC 5451](http://www.ietf.org/rfc/rfc5451.txt)
[RFC 7001](http://tools.ietf.org/html/rfc7001#section-3)

{'fraction_non_alphanumeric': 0.16189536031589338, 'fraction_numerical': 0.018427114182296808, 'mean_word_length': 2.872611464968153, 'pattern_counts': {'":': 0, '<': 3, '<?xml version=': 0, '>': 3, 'https://': 0, 'lorem ipsum': 0, 'www.': 4, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
{'dir': 'git-commits-cleaned', 'id': '2205102', 'n_tokens_mistral': 927, 'n_tokens_neox': 839, 'n_words': 373}