Smtpd spam prevention

Smtpd spam prevention

[sirjofri]

Hello all,

my smtpd server runs fine, but I recently got some spam mails. Currently 
my server doesn't filter anything and does nothing to prevent spam.

There are two options to smtpd, according to the man:

> -D sleeps for 15 seconds usually at the start of the SMTP
> dialogue; this deters some spammers.  Connections from
> Class A networks frequented by spammers will incur a
> longer delay.

> -g turns on grey/white list processing.  All mail is
> rejected (with a retry code) unless the sender's IP
> address is on the whitelist, /mail/grey/whitelist, an
> append only file.  Addresses can be added to the whitel-
> ist by the administrator.  However, the usual way for
> addresses to be added is by smtpd itself. ... (Greylisting)

Both options make sense to me. -g might work out of the box, is there 
anything I need to know before enabling it?

-D is new to me. I never heard about this extra delay when handling mail. 
Can I safely enable that?

What configurations do you use?

I don't want to dive into ratfs for now. My mail traffic is low anyways.

sirjofri

Re: [9front] Smtpd spam prevention

[Stanley Lieber]

On November 20, 2020 10:53:35 AM EST, sirjofri <sirjofri+ml-9front@sirjofri.de> wrote:
>Hello all,
>
>my smtpd server runs fine, but I recently got some spam mails.
>Currently 
>my server doesn't filter anything and does nothing to prevent spam.
>
>There are two options to smtpd, according to the man:
>
>> -D sleeps for 15 seconds usually at the start of the SMTP
>> dialogue; this deters some spammers.  Connections from
>> Class A networks frequented by spammers will incur a
>> longer delay.
>
>> -g turns on grey/white list processing.  All mail is
>> rejected (with a retry code) unless the sender's IP
>> address is on the whitelist, /mail/grey/whitelist, an
>> append only file.  Addresses can be added to the whitel-
>> ist by the administrator.  However, the usual way for
>> addresses to be added is by smtpd itself. ... (Greylisting)
>
>Both options make sense to me. -g might work out of the box, is there 
>anything I need to know before enabling it?
>
>-D is new to me. I never heard about this extra delay when handling
>mail. 
>Can I safely enable that?
>
>What configurations do you use?
>
>I don't want to dive into ratfs for now. My mail traffic is low
>anyways.
>
>sirjofri

never used -g or -D.

I ran ratfs for a while. i inadvertently blocked a lot of legit mail as well. I got tired of maintaining it.

I update /mail/lib/spamhaus every night via cron.

I do manually block some repeat offender class c blocks with -k.

sl

Re: [9front] Smtpd spam prevention

[ori]

Quoth sirjofri <sirjofri+ml-9front@sirjofri.de>:
> Hello all,
> 
> my smtpd server runs fine, but I recently got some spam mails. Currently 
> my server doesn't filter anything and does nothing to prevent spam.
> 
> There are two options to smtpd, according to the man:

I still have to mess with it, but there's also some undocumented
bayesian filtering and spf validation that you can use from a
pipeto, with examples in /mail/lib.

I'm still running my mail server on OpenBSD, since I do rely on
it for a bunch of important things -- but I think I'll be taking
the next while to gradually migrate over.

Re: [9front] Smtpd spam prevention

[Steve Simon]

spamaus is the way to go.

greylisting doesn't help much these days, spam bots are better written than they used to be.

-Steve

> On 20 Nov 2020, at 4:45 pm, ori@eigenstate.org wrote:
> 
> Quoth sirjofri <sirjofri+ml-9front@sirjofri.de>:
>> Hello all,
>> 
>> my smtpd server runs fine, but I recently got some spam mails. Currently 
>> my server doesn't filter anything and does nothing to prevent spam.
>> 
>> There are two options to smtpd, according to the man:
> 
> I still have to mess with it, but there's also some undocumented
> bayesian filtering and spf validation that you can use from a
> pipeto, with examples in /mail/lib.
> 
> I'm still running my mail server on OpenBSD, since I do rely on
> it for a bunch of important things -- but I think I'll be taking
> the next while to gradually migrate over.