[Dovecot] v2.2 status update: IMAP NOTIFY extension and more

[Cor Bosman]

>> What would be really cool is if you also kept statistics on certain metrics, like how many emails a specific sender has sent. If this is done right, it could become a centralised spam sender back-off system over multiple smtp servers. Maybe something for the future. We now pay $$$$ for a commercial system that implements this. 
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> The submission servers would need to share state with each others to make this reliable. Some nosql database would work for that I guess (memcached?)
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> Can you describe more fully what you would want it to do and/or what the current system does? Probably not something I'll implement soon, but would be good to know for future :)

They would indeed need to share the state, this is what the commercial system does (Cloudmark Gateway). The idea is to prevent senders to send email beyond certain limits that are configurable. Lets say, 200 emails in a minute, or 500 an hour, or whatever. Of course allowing for whitelists. With ever increasing speeds of residential connections (we have hundreds of fiber connections now, growing rapidly), these become very fast spam sources without something to keep them in check. It's easy on 1 server, not so easy if you have dozens of smtp servers.  

But yes, something for a distant future :) And CM has other features as well, so it may not be so easy to replace :)

Cor