[CentOS] Configuring sendmail in a corporate environment

lingu hicheerup at gmail.com
Tue Jul 1 14:40:41 UTC 2008


  First of all check the connectivity from that server to the external
domains like gmail,yahoo.com by doing telnet on port 25.if  u get connected
then then ur firewall is not blocking any outgoing port 25 connection.

  Then you have to check one more parmeter.If your domain  on ur sendmail
server is registered with the internet then only you can send a mail to any
external domains.If you are not registered your ip wil get blacklisted in
the spam database.

 Incase if your are registered if it is an direct mx then no need to set any
relay server parameter in sendmail.Incase your MX is pointed to some third
party then you have to tell the relay server ip in sendmail mc file.it wll
be some thing like below

dnl define(`SMART_HOST', `smtp.your.provider')dnl

Replace smtp.your.provider with mx2.example.com,this is where your mx get
pointed so that all of your outgoing mails will relayed via this server.

dnl define(`SMART_HOST', `mx2.example.com')dnl

Note: check the connectivity from that centos sendmail server to
mx2.example.com first for port 25 connection.


On Tue, Jul 1, 2008 at 7:05 PM, Alfred von Campe <alfred at von-campe.com>

> I have a stock CentOS 5 system as far as email (sendmail) is concerned that
> is on our corporate LAN.  I am not trying to set up a mail server; I merely
> want our CentOS systems to be able to send out emails.  This works as long
> as the recipient's domain is our local domain.  Any email send to recipients
> that are not in our local domain get stuck in the queue:
> # mailq
>                /var/spool/mqueue (2 requests)
> -----Q-ID----- --Size-- -----Q-Time-----
> ------------Sender/Recipient-----------
> m61D6wC1029257       16 Tue Jul  1 09:06 <XXXX at XXXX.XXXX.com>
>                 (Deferred: Connection timed out with mx2.emailsrvr.com.)
>                                         <alfred at von-campe.com>
> It appears that our firewall is not allowing connection to outside MX
> hosts.  I think I need to configure sendmail to forward emails to our local
> smtp host, but I am not sure how to do that.
> Alfred
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