After reading Antonio Prado’s Reverse DNS lookup for Italian Government’s mail exchangers post I got intrigued by the idea of checking how many of those Italian Government’s MX mail servers support STARTTLS.
STARTTLS “offers a way to upgrade a plain text connection to an encrypted (TLS or SSL) connection” (Wikipedia) and, when it’s implemented on the MX SMTP server, it allows a STARTTLS-aware user’s outbound mail server to encrypt the traffic toward the recipient’s server.
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The public DNSBL services offered by AHBL have been shutdown.
Services and programs which used dnsbl.ahbl.org, ircbl.ahbl.org and rhsbl.ahbl.org need to be updated in order to avoid false positives:
X-Spam-Status: No, score=0.789 tagged_above=-999 required=6
Spamassassin configuration, for example, needs to be fixed:
# cat /usr/share/spamassassin/20_dnsbl_tests.cf | grep AHBL
header DNS_FROM_AHBL_RHSBL eval:check_rbl_envfrom('ahbl', 'rhsbl.ahbl.org.')
describe DNS_FROM_AHBL_RHSBL Envelope sender listed in dnsbl.ahbl.org
tflags DNS_FROM_AHBL_RHSBL net
Comment that block or (at least) force a score zero for the rule in your local configuration:
# cat /etc/spamassassin/local.cf | grep AHBL
score DNS_FROM_AHBL_RHSBL 0
It seems that, under certain conditions, GMail reports failed SPF checks for messages fetched via POP3 from other mail servers.
I noticed this behaviour on messages received, for example, by mail servers where an internal relay is used, like the following message sent from PayPal (which uses an hard-fail policy):
Received-SPF: fail (google.com: domain of email@example.com does not
designate A.B.C.D as permitted sender) client-ip=A.B.C.D;
Received: by 10.64.225.172 with POP3 ...
X-Gmail-Fetch-Info: MYSELF@MYDOMAIN.TLD 3 pop3.MYDOMAIN.TLD
Received: from server1.MYPROVIDER.TLD (A.B.C.D)
by server2.MYPROVIDER.TLD with SMTP; ...
Received: from outbound.emea.e.paypal.com (184.108.40.206)
by mx1.MYPROVIDER.TLD with SMTP; ...
From: "PayPal" <firstname.lastname@example.org>
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I’m happy to see that more and more tools are developed to increase the security level and trustworthiness of Internet applications. I already talked about DNSSEC and tools to check the validity of domain names, many others blogged about DANE and TLSA validation support in browsers; this time I would like to focus on DKIM and on a Thunderbird add-on to verify its signatures taking advantage of DNSSEC end-to-end validation.
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