[CentOS] Anyway to ensure SSH availability?

Thu Jun 30 08:43:36 UTC 2011
Ljubomir Ljubojevic <office at plnet.rs>

Robert Heller wrote:
> If the machine is a public-facing smtp server, I would look first to see
> if you are getting the problem I was having.  Maybe looking at the
> maillog to see if the volume of incoming mail is just overwhelming the
> system. In which case you need to do things to keep sendmail from
> running to many processes, either by throttling the connection rate and/or
> be using the accessdb to discard or reject connection from known problem
> networks. 
> 

Very simple solution is to implement Reverse DNS check. My Postfix mail 
server refuses to accept any mail from FQDN without valid reverse DNS. I 
(was?) also use graylisting and few other measures, but Reverse DNS 
helped immensely in lowering SPAM that comes to my mailboxes. I would 
say that reduction is some 70-80%.

Ljubomir