Wed, 07 May 2014
GMail Spam Filter
Apparently, GMail spam filter got too zealous. I have my own domain, and I run my own SMTP server on it. Now it seems Google has decided to reject all mail from my server:
<my.test.gmail.account@gmail.com>: host
gmail-smtp-in.l.google.com[2a00:1450:4013:c01::1b] said: 550-5.7.1
[2a01:...my.ipv6.address...] Our system has detected that this
550-5.7.1 message is likely unsolicited mail. To reduce the amount of spam
sent 550-5.7.1 to Gmail, this message has been blocked. Please visit
550-5.7.1 http://support.google.com/mail/bin/answer.py?hl=en&answer=188131
for 550 5.7.1 more information. o49si12858332eef.38 - gsmtp (in reply to
end of DATA command)
In the mentioned page, they recommend putting "SPAM" in the subject of forwarded mail :-/ in order to trick GMail to accept it. But then, it is not forwarded mail at all, it is mail originated on the same host from which the SMTP client is trying to send it to GMail.
So, are we getting to the world where only Google and few other big players are allowed to run their own SMTP servers? And after that, they wil "suddenly" decide to stop talking to each other, as we have seen in the XMPP case with Google Talk. The morale of the story is: don't rely on services you cannot control for your private data and communication. They will drop your incoming mail as supposed spam and you will not be able to do anything about it.
Update - Wed, 21 May 2014: Workaround Available
Apparently, this is indeed IPv6-related, and the workaround is either to use IPv4 for Gmail, or better, make Postfix fall back to IPv4 after trying IPv6 first. This way, Google gets a penalty of two connections, and hopefully will have motivation to fix their problem.
The solution is described here, and more can be read in the postfix-users list archive (another source). The solution is:
Add the following to /etc/postfix/main.cf:
smtp_reply_filter = pcre:/etc/postfix/smtp_reply_filter
Create a file named /etc/postfix/smtp_reply_filter with
the following line:
/^5(\d\d )5(.*information. \S+ - gsmtp.*)/ 4${1}4$2
and reload the Postfix configuration using postfix reload command.