Is having a SMTP server truly necessary?

Hello,

I was wondering, is having an active SMTP server on your system truly
necessary? I notice a SMTP server comes with every major linux distribution.

I *do* need the ability to send mail to the internet at times (my log files
through a cron job more specifically) as well as receive mail locally.

I ideally would like to remove it, because it's one more thing to go
wrong/broken into. I am not expecting to have mail received from the outside
internet.

- Steve

Steve Quezadas wrote:

> Hello,
>
> I was wondering, is having an active SMTP server on your system truly
> necessary? I notice a SMTP server comes with every major linux
> distribution.
>

You do need an MTA (mail server) for local (system) mail, e.g. the cron jobs
you describe. An MTA more than SMTP, and that's why it needs to be kept.

Postfix
Qmail
Exim
Sendmail

Those are the normal MTA's. In your case, you want to keep one installed.
What you can do is configure your system to only send and receive mail for
the local system. Most distributions have this configuration for the MTA.

In the MTA, SMTP is the protocol that receives remote mail from clients.
You send messages via SMTP to remote servers that accept the SMTP
connection. You can configure the MTA to NOT accept requests for SMTP
transfers (i.e. turn off the SMTP receiving feature).

You can also turn off the MTA's ability to send mail via SMTP (i.e. turn off
the ability to act as a client). This is not desired if you wish to send
mail via the MTA. Mail clients such as KMail and Evolution can send mail
via SMTP without the help of an MTA. System tools such as cron need an MTA
to send mail to remote addresses via SMTP.

You can firewall off the MTA ports, deny requests for an MTA through
/etc/hosts.deny and /etc/hosts.allow, and, in the MTA's config file(s), you
can turn off the features that accept incoming remote connections. But the
MTA is still there for your system mail.

D W wrote:

> Steve Quezadas wrote:
>
>> Hello,
>>
>> I was wondering, is having an active SMTP server on your system truly
>> necessary? I notice a SMTP server comes with every major linux
>> distribution.
>>
>
> You do need an MTA (mail server) for local (system) mail, e.g. the
> cron jobs
> you describe. An MTA more than SMTP, and that's why it needs to be
> kept.
>
> Postfix
> Qmail
> Exim
> Sendmail
>
> Those are the normal MTA's. In your case, you want to keep one
> installed. What you can do is configure your system to only send and
> receive mail for
> the local system. Most distributions have this configuration for the
> MTA.
>
> In the MTA, SMTP is the protocol that receives remote mail from
> clients. You send messages via SMTP to remote servers that accept the
> SMTP
> connection. You can configure the MTA to NOT accept requests for SMTP
> transfers (i.e. turn off the SMTP receiving feature).
>
> You can also turn off the MTA's ability to send mail via SMTP (i.e.
> turn off
> the ability to act as a client). This is not desired if you wish to
> send
> mail via the MTA. Mail clients such as KMail and Evolution can send
> mail
> via SMTP without the help of an MTA. System tools such as cron need
> an MTA to send mail to remote addresses via SMTP.
>
> You can firewall off the MTA ports, deny requests for an MTA through
> /etc/hosts.deny and /etc/hosts.allow, and, in the MTA's config
> file(s), you
> can turn off the features that accept incoming remote connections.
> But the MTA is still there for your system mail.


In other words, he does not need an SMTP server if he is running a
workstation and is not handline outgoing mail for other machines.
He does need exim or postfix or qmail or - God help us - sendmail.

In article <D6kPa.40424$(E-Mail Removed) ink.net>,
"Steve Quezadas" <(E-Mail Removed)> writes:
>
> I was wondering, is having an active SMTP server on your system truly
> necessary? I notice a SMTP server comes with every major linux distribution.

Chances are you don't need an SMTP server per se; but most Linux
distributions do include utilities (security checking tools, for
instance) that assume you've got some sort of mail transfer agent (MTA)
installed, typically available under the name "sendmail". (Other mail
servers, such as Postfix and Exim, usually include binaries or links of
this name.)

Typically, packages such as sendmail, Postfix, and Exim, are run as SMTP
servers, but they don't need to be run in that way (that is, run as
daemons and bound to listen to port 25). Instead, they can be installed
but not started at runtime, and instead handle local mail delivery only
when they're called as ordinary local programs. I believe some
distributions now use this sort of configuration as the default, but I
don't recall which work in this way and which use the more traditional
SMTP server approach. Some distributions also run the SMTP server in
daemon mode, but bind it only to the localhost (127.0.0.1) address or
otherwise restrict its ability to handle connections from other systems.

Overall, I wouldn't recommend trying to completely uninstall the MTA (via
"rpm -e sendmail" or some similar command), but you might investigate how
yours is configured to run and perhaps reconfigure it. The details will
differ from one distribution and MTA to another.

--
Rod Smith, (E-Mail Removed)
http://www.rodsbooks.com
Author of books on Linux, FreeBSD, and networking