CentOS - Jul 2008 - Configuring sendmail in a corporate environment

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

On Jul 1, 2008, at 9:35 AM, Alfred von Campe wrote:
> 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.

1. make sure /etc/mail/sendmail.mc includes the following line:

define(`SMART_HOST', `your.local.smtp.host')dnl

as well as whatever other configuration is necessary for your site.

2. cd /etc/mail; make sendmail.cf; service sendmail restart

-steve

p.s. it is easier to configure Postfix to do this; the instructions  
are provided in the comments of /etc/postfix/main.cf.

--
If this were played upon a stage now, I could condemn it as an  
improbable fiction. - Fabian, Twelfth Night, III,v

Alfred von Campe wrote:
> 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.
In my write up of using sendmail with gmail I think I explain how
to rewrite the from. If it's not there then look at the Sendmail/
Comcast write up:

http://www.linuxha.com/other/sendmail/gmail.html

I had to rewrite the from as being from gmail.com in order for
gmail.com to accept the mail.

-- 
Linux Home Automation         Neil Cherry       ncherry at linuxha.com
http://www.linuxha.com/                         Main site
http://linuxha.blogspot.com/                    My HA Blog
Author of:    	Linux Smart Homes For Dummies

>> 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.
>>     
Best to do that anyway. Some e-mail providers will only accept e-mail 
from known mail servers (AOL)
and bounce if the IP of your sending server is not a static, known 
mailserver.

What you want is 'SMARTHOST'.

DSmy.mail.server.com        in sendmail.cf

or

define(`SMART_HOST', `my.mail.server.com')dnl       in sendmail.mc
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Hi.

  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.


Regards,
lingu


On Tue, Jul 1, 2008 at 7:05 PM, Alfred von Campe <alfred at von-campe.com>
wrote:
> 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
>
> _______________________________________________
> CentOS mailing list
> CentOS at centos.org
> http://lists.centos.org/mailman/listinfo/centos
>
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Alfred von Campe wrote:
> Thanks for all the quick responses.  Enabling SMART_HOST as well as 
> masquerading did the trick.  I also had to install the sendmail-cf 
> RPM, but everything appears to be working now.
You CAN manage without sendmail-cf RPM by editing the config file by 
hand. I wouldn't try it without a good psychiatrist and lots of
medication to hand though! Goodness only knows what the sendmail guys 
were thinking of when they defined the config file specification.

Anyway, good to see you get it going.