Unable to email anyone from my primary domain name; thanks Google Mail and G Suite.

Thu Oct 24 21:10:46 UTC 2019

You're assuming that IPv6 is at fault, but as I've already mentioned, if I
change the From and MAIL FROM to one of the other domains with a DNS zone
similar to the primary one with crontab-acquired "very low reputation",
without changing anything else, then the identical messages do get through
at the SMTP stage — and show up directly in Inbox — i.e., don't even end up
in the Spam folder, either.

So, sorry, but I'm not going to go around blocking my IPv6 for no reason.

C.

On Thu, 24 Oct 2019 at 07:41, Alain Hebert <ahebert at pubnix.net> wrote:

>     "Trust Andrew(tm) when I say this."
>
> Disable your IPv6 access to their mail server.
>
>     At Google, something hasn't worked, well since the beginning of time,
> when it come to propagating your domain reputation to <something> handling
> incoming emails using IPv6.
>
>     I just had the case last week when a customer account go abused and
> dropped their domain reputation to 0 for GMail/GSuite.  Nothing worked
> until I made outgoing emails connection "icmp unreachable" thru IPv6.
>
>     Example with ipfw.
>
> ipfw add [rule number] reject ip6 from me6 to any 25
> ipfw add [rule number] reject ip6 from me6 to any 587
>
>     Good luck.
>
> -----
> Alain Hebert                                ahebert at pubnix.net
> PubNIX Inc.
> 50 boul. St-Charles
> P.O. Box 26770     Beaconsfield, Quebec     H9W 6G7
> Tel: 514-990-5911  http://www.pubnix.net    Fax: 514-990-9443
>
> On 2019-10-23 20:18, Constantine A. Murenin wrote:
>
> Dear NANOG@,
>
> I'm not sure where else to post this, and this is not really new, either,
> but I think I have a new take here.
>
> I use my own personal domain name for various UNIX stuff, including
> sending log-related things to myself out of cron, which end up in my own
> Gmail.com account, either directly, or through forwarding (w/o SRS).  (I do
> not use G Suite for my own domain name, for obvious reasons; just the
> consumer-based gmail.com email address from the old times of
> invitation-based registrations.)
>
> Over the years, I sometimes had certain messages rejected by Gmail, but it
> was a very low rate of rejection (less than 5% for any mail I cared about),
> and wasn't a major problem (usually only some automated messages would be
> rejected).
>
> A couple of months ago, I setup some new scripts that would send me new
> nightly emails.  It's all plain text, but had a few dozen of domain names
> present (it's logs).  Absolutely no links, just plenty of domains which I
> don't control.  So, Gmail has been presenting most of these messages with
> their red warning label that the email contains malicious links, even
> though all of these emails contained zero links, zero URLs to any of these
> unknown domain names, zero URL schemes, zero "http://", zero "https://"
> etc.  You get the idea.
>
> Since about a few weeks ago, I am now seeing at least a 95% rejection rate
> for my domain name, for ALL email, including the forwards.  Including
> emails which I send to myself from within Google, and which get forwarded
> back to Gmail by my UNIX machine (which is not known to break Gmail's DKIM,
> either, although it's also difficult to test, because when it does get
> through, it's automatically marked as a duplicate by Gmail, so, you don't
> get DKIM status from Gmail by looking at the headers, since you only get to
> examine the original copy that was sent, not the forwarded duplicate that
> was subsequently accepted).  I.e., emails with a passing DMARC still get
> rejected.
>
> The funny thing is, Google doesn't actually blacklist my primary IPv6
> address in my own /48 from which all of my messages originate; even though
> the rDNS resolves to a subdomain on the very same domain name which they've
> blacklisted "due to the very low reputation".  They've blacklisted just the
> main domain name that I use for my own non-Gmail-hosted mail.  Sending the
> same messages into my Gmail.com from a different domain name in MAIL FROM,
> which is served from the same zone file DNS-wise (e.g., an SPF pass),
> through sendmail's `-f` option, or with Mutt, makes the messages go through
> (even with rDNS being "low reputation"); sending it from my primary domain
> name in MAIL FROM results in the following:
>
> >>> DATA
> <<< 550-5.7.1 [2001:470:xxxx::      19] Our system has detected that this
> message is
> <<< 550-5.7.1 likely suspicious due to the very low reputation of the
> sending
> <<< 550-5.7.1 domain. To best protect our users from spam, the message has
> been
> <<< 550-5.7.1 blocked. Please visit
> <<< 550 5.7.1  https://support.google.com/mail/answer/188131 for more
> information. 135si403977wma.43 - gsmtp
> 554 5.0.0 Service unavailable
>
> The support article suggests using Postmaster Tools; great, never heard of
> it, sounds cool; let's verify our domain, and try it out, hopefully,
> there's a solution right there.
>
> However, after verifying my domain name through DNS for Postmaster Tools,
> it is revealed that Postmaster Tools cannot tell me anything at all, with
> all tabs and screens being 100% blank, allegedly because I'm not actually a
> mass email sender (I don't send hundreds of emails a day or whatnot), and
> they're too afraid that I'll figure out why my mail doesn't actually go
> through, instead of signing up for G Suite.
>
> Right now, I've had a business need to reply to a work-related email from
> some other business.
>
> This is what I got after sending my reply from my primary domain name
> through mutt — a nice double rejection by both the G Suite and Gmail in a
> single bounce generated by my server:
>
>
>    ----- Transcript of session follows -----
> ... while talking to aspmx.l.google.com.:
> >>> DATA
> <<< 550-5.7.1 [2001:470:xxxx::      19] Our system has detected that this
> message is
> <<< 550-5.7.1 likely suspicious due to the very low reputation of the
> sending
> <<< 550-5.7.1 domain. To best protect our users from spam, the message has
> been
> <<< 550-5.7.1 blocked. Please visit
> <<< 550 5.7.1  https://support.google.com/mail/answer/188131 for more
> information. z11si12494671wrw.137 - gsmtp
> 554 5.0.0 Service unavailable
> ... while talking to gmail-smtp-in.l.google.com.:
> >>> DATA
> <<< 550-5.7.1 [2001:470:xxxx::      19] Our system has detected that this
> message is
> <<< 550-5.7.1 likely suspicious due to the very low reputation of the
> sending
> <<< 550-5.7.1 domain. To best protect our users from spam, the message has
> been
> <<< 550-5.7.1 blocked. Please visit
> <<< 550 5.7.1  https://support.google.com/mail/answer/188131 for more
> information. 135si403977wma.43 - gsmtp
> 554 5.0.0 Service unavailable
>
>
> Changing MAIL FROM into a non-primary domain name (served out of an
> identical zone file, basically) gets the message accepted, without DKIM,
> without the 4-minute delay that many "suspicious" messages have had for
> months now, from the very same IPv6 address with the rDNS pointing to the
> domain name with "the very low reputation", and it shows up in both my own
> Gmail as well as, presumably, in the G Suite account of the business
> partner I was replying to.  (Note that this trick where the rDNS domain
> gets ignored works only for new emails with a passing SPF; I presume the
> rDNS still prevails in bringing the "low reputation of the sending domain"
> for forwards, as they don't seem to succeed any longer now.)
>
>
> There are a number of possible tl;dr: takeaways here:
>
> * don't spread the monoculture — don't use G Suite for your organisation;
>
> * don't send crontab output to your Gmail from your primary domain name;
>
> * don't use Gmail.
>
>
> What is my own takeaway here?
>
> * Without being an anti-Google zealot, from a purely practical
> perspective, since my Gmail account no longer contains the mail I care most
> about, as it gets rejected on the SMTP layer, I'll have fewer reasons to
> use it.
>
> * I'll now have no other choice but to modify my setup to stop forwarding
> to Gmail, because my business contacts don't need to see all these bounces
> that are now taking place.
>
> * Since so many businesses are G Suite useds, I'm still looking for a
> solution to get rid of the "the very low reputation of the sending domain"
> from a domain name I've been using since 2007, and which I'm 100% convinced
> was blacklisted by Google entirely for me sending crontab with system logs
> (zero HTML, zero URLs) to my own Gmail.  I have SPF and DMARC all setup and
> passing since years ago, which doesn't stop this issue from occurring.
> Merely switching the name of the domain in From and MAIL FROM to any other
> domain I own (which points to the very same MX) appears to be my workaround
> for now.
>
>
> Some possible suggestions for Google, if I may:
>
> * Maybe don't convert schemeless domain names which are non-URLs into
> "malicious" URLs?  (They already do seem to block them from being presented
> as links in the UI in such an instance, but there's little reason for
> trying to convert these domain names into links in the first place.)
>
> * Maybe don't consider harmless plain text emails with a bunch of domain
> names to contain malicious links when they don't?
>
> * Maybe don't assume everyone with a domain name runs a G Suite?  (Their
> whole troubleshooting guide is built around it.)
>
> * Maybe don't assume everyone with a domain name sends hundreds of emails
> from their domain name per day?  (They seem to limit Postmaster Tools based
> on such a criterion.)
>
> * Maybe don't blacklist a domain name for sending harmless logs to a Gmail
> account that lists said domain name as an alternative From address?
>
>
> Cheers,
> Constantine.
>
>
>
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