Hi Gregory
Thanks for your advice.
Since we don’t want sent mass of mails (excepted some newsletter with about 50-100 addresses, which
I will not declare as mass mails), the first 3 points are perhaps overkill for us.
4) I’ll check for.
5) This are setup correct
6) Since the spammer didn’t reconnect from the same ip, this would not help. The
spammer connected every time from an other ip and just sent out a few (20-30) mails, that
looks almost normal to the mail server.
6 II) We will check, if we can implement something like this, which will sent an alert to us.
7) As Rainer has written, I also think, that the password has been stolen or be track by
some kind of Trojan. So, strong password will note help here.
8) What do you mean, when you say Follow-up the other reputation systems???
9) Since this only happen one time for some years, I prefer something like 6 II)
Blocking Port 25 would be that fine. Our customer have contact over the whole world, so blocking
Port 25 would be a solution. And some of the connection was coming from Italy or Germany, that
will even not help (IMHO this aren’t exotic countries ;-).
Kind Regards
Parick
Von: Gregory Agerba [mailto:gregory.agerba@gmail.com]
Gesendet: Mittwoch, 23. Juni 2010 16:51
Hi Patrick,
>From my past experience delivering very often very big newsletters...
Some advices to deliver mass of mails:
1) Distribute your email out of 4-5 virtual interfaces (like Exim would let you do) and rotate them every x hours or/and randomly.
2) Use different domain names not only FQDNs (this is what mailchimp.com does to distribute their millions of emails).
3) Use specific IPs for specific large domains, like Gmail, Yahoo, Hotmail and rotate them every once in a while.
4) Sign-up for loopback feed and monitor the complaint box constantly. Yahoo and such big got that for free.
5) Ensure you have proper RDNS, SPF and DKIM setup.
6) Use iptablesand custom rulesets to block above a certain amount of SMTP connections per host on port 25/587.
6) Count your outgoing average email you send a day/ per hour, put some cron that grep/cat/wc the logs, with threshold that triggers alarms.
7) Educate your users for strong passwords.
8) Follow-up the other reputation systems like Cisco, Barracuda, Fortinet, etc..
9) Use dedicated IP for strange or doubtful clients.
10) Mind shared IPs.
You can also block port 25 from exotic countries that you do not expect to send you emails, but they are a liability and its quite mean.
Gregory
2010/6/23 Patrick Studer <p.studer@x-netconsulting.ch>
Hi Mickey
That is what we already thinking about, to implement a second server on a different ip. At the other
hand, I don’t think that’s way I want to go.
Since this is the first time within some years, I will check, if there is an other way to solve this issue.
Kind Regards
Patrick Studer
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