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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