Re: [Fail2ban-users] Drop Established Connection on Ban

[Kenneth P. <sh...@se...>]

--On Monday, May 03, 2021 2:05 PM +0100 Darac Marjal 
<mai...@da...> wrote:

> If sendmail can't do that (I'm struggling to find
> decent documentation for it), consider replacing sendmail with exim or
> postfix - both of which DO have this capability.

I learned sendmail using the "bat book" from O'Reilly. (Popular publisher 
of books on open source systems, with each book characterized by a notable 
animal on the cover.)

<https://www.oreilly.com/library/view/sendmail-4th-edition/9780596510299/>

Alas, the online documentation got much harder to find when sendmail went 
commercial. Some FAQs here:

<https://www.proofpoint.com/us/sendmail/faq>

Alas, sendmail was written at a time when the Internet was more trusting 
and when software was less integrated, so authentication was bolted on as 
an extra feature. I haven't found anything on rate-limiting it except as an 
anti-spam measure.

Note that Red Hat distros switched to Postfix as the default mail server a 
couple versions back but still provide sendmail as an alternative. So a 
recent Fedora or CentOS system will likely be running Postfix.