[CentOS] Sending Email Via Telnet

[Les Mikesell]

On Tue, Oct 16, 2012 at 11:10 AM, Steven Tardy <sjt5 at its.msstate.edu> wrote:
> is any email program running?
> run:
>    netstat -pant|grep ":25"|grep LISTEN
> to see if any program is listening... output should look like:
>   tcp 0 0 0.0.0.0:25 0.0.0.0:* LISTEN 21493/sendmail
>
> guess it'll say 'postfix' or 'master' instead of 'sendmail' on RH6.

How long are you waiting for a response to appear?  Mailers do an
assortment of reverse-dns lookups and perhaps an ident query to the
source before responding.   If you firewall these with a 'drop'
instead of 'reject' you leave the application hanging for fairly long
timeout.  And some mailers have a config option for an intentional
delay before their first message and will drop the connection it the
other end sends first (snmp protocol requires the connecting host to
wait).    Also, you should have something showing up in
/var/log/mailllog about the connections.

-- 
   Les Mikesell
      lesmikesell at gmail.com