> On Fri, Aug 02, 2019 at 02:43:30PM -0400, Fred Smith wrote:
>> On Fri, Aug 02, 2019 at 02:38:05PM -0400, Jon LaBadie wrote:
>> > On Fri, Aug 02, 2019 at 10:19:49AM -0400, mark wrote:
>> > > Fred Smith wrote:
>> > > > On Fri, Aug 02, 2019 at 09:28:23AM -0400, mark wrote:
>> > > <MVNCH>
>> > > > One thing I don't understand is how/why the firewall is DROPping
>> so
>> > > > many attempts on port 25 when it in fact has a port forward rule
>> sending
>> > > > port 25 on to my mailserver. How does it know, or why does it
>> think that
>> > > > some of them can be dropped at the outer barrier?
>> > > >
>> > > >> you, but thank you for taking a hundred thousand or so for all of
>> us.
>> > > >
>> > > > Hey, its the least I can do for all the good guys out there! :)
>> > > > But that doesn't mean the same dratsabs aren't hitting all the
>> rest
>> > > > of you too.
>> > > >
>> > > I'm sure they are. Are you running fail2ban?
>> > >
>> > Several years back I switched from sendmail to postfix.
>> > Not knowing what I was doing, I think I have it set to
>> > say it will forward email following SASL authentication.
>> > But as I had no intention of forwarding anything, I did
>> > not set up any authentication methods. So anyone who
>> > tries fails to authenticate.
>> >
>> > With fail2ban in place I get 200-500 daily SASL "fail to
>> > authenticate" instances. In contrast, several months ago
>> > fail2ban either died or did not restart correctly. This
>> > went unnoticed for about a week. During that time I got
>> > 10000-32000 daily "failed to authenticate".
>>
>> I'm not using fail2ban, and am using sendmail (why? because
>> I've spent years slowly accumulating options in my .mc file that
>> kill off unwanted connections and other hate-the-spammer options.).
>> I'm not getting such emails but most of the entries in /var/log/mail
>> are due to such events. every now and then a legitimate email can
>> be seen passing through.
>>
>> Oh, I also am now using (as of 2-3 years ago) milter-greylist, which
>> made an enormous contribution to preventing spam emails.
>>
>> Fred
>
> I tried greylisting a while back and was surprised how many were
> being rejected. But they were also getting through despite the
> rejection at my end.
>
> I use a 3rd party as my backup MX email address. If I'm down,
> they save up the email and forward it to me when I'm back up.
> But the greylist rejected emails just tried the backup MX
> address and got through that way.
>
> Should I ever have a backup MX that I administer, I will
> definitely reinstate greylisting.
If you have a stable environment and connections, you could also get rid
of the backup MX completely. That's what we did and we're not alone. Of
course if you have frequent service interruptions for whatever reason,
that's not an option.
Regards,
Simon
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