Configuring Sendmail

Ok, let's now start up the "sendmailconfig" script, and go through the configuration settings: /etc/init.d/sendmail start sendmailconfig.

debian:~# sendmailconfig

Sendmail Configuration
By answering the following questions, you can \
                configure sendmail for your
system. Default values are determined either by \
                your existing configuration
or from common usage.

Press [ENTER] 

Mail Name
Your 'mail name' is the hostname portion of \
                the address to be shown on
outgoing news and mail messages (following \
                the username and @ sign).  This
name will be used by other programs besides \
                sendmail; it should be the single,
full domain name (FQDN) from which mail \
                will appear to originate.

Mail name? [] 

This is identical to the Exim configuration section in this that we covered previously.

Null Client
A special configuration known as the "null client" \
                can be created for this
host if all mail should be forwarded to a \
                central hub via a local SMTP-based
network. This may be a suitable configuration \
                if you want to forward all of
your mail to your local Internet service \
                provider (ISP) for delivery.

To enable this option, give the name of the \
                host to which all mail should be
forwarded. Otherwise leave the option \
                empty to disable it.
To remove a prior name, use 'NONE'.

Null client forward host? [] 

A "null client" configuration is suitable for a workstation or similar system, which simply needs to redirect all its e-mail to the central mail server on your network. we'll leave this blank for our current configuration.

Smart Host
A "Smart Host" is one that can deliver mail to \
                external machines.  By using
a "Smart Host", we don't need DNS, or good \
                connectivity ourselves.  This is
most likely what you want if you have a \
                dialup link, or sit behind a firewall.

To enable this option, give the name of the \
                host to which all non-local mail
should be forwarded.  Otherwise leave \
                the option empty.
To remove a prior name, use 'NONE'.

Smart Host:? [] 

A "smart host" configuration is similar to a "null client", except it also does not require permanent connectivity to the Internet. This is a good choice if you connect to the Internet using a dial-up connection. we'll leave this option blank for our current configuration.

Address Canonification
Usually sendmail will canonify all addresses by \
                consulting a name server and
resolving hosts to their fully qualified domain \
                name (FQDN). Under special
circumstances you may want to disable this \
                feature, for example if this
machine acts only as a mail gateway.

Disable address canonification? [N] 

We will leave address canonification enabled. This is analogous to Exim's "qualify_domain" option.

SMTP Mailer
If you plan to exchange mail with other computers, \
                you should enable the
SMTP mailer. Even if you don't plan to exchange \
                mail with other computers,
it is still a good idea to enable this so local \
                programs can use it.

Enable the SMTP mailer? [Y]

As recommended, we will enable the SMTP mailer.

Masquerade Envelope
If you want mail envelopes (as well as mail \
                headers) to appear to come from
'', you can enable this option.

Masquerade envelopes? [Y] 

This is useful if your mail server is called "", but you wish for your outgoing e-mail to appear as if it is coming from "". You will normally want to enable this.

All Masquerade
If enabled, this feature will cause recipient \
                addresses to also appear to come
from ''. Normally they get the \
                local hostname.
Although this may be right for ordinary users, \
                it can break local aliases. For
example, if you send to "localalias", the \
                originating sendmail will find that
alias and send to all members, but send \
                the message with
"To:". Since that \
                alias likely does
not exist, replies will fail. Use this feature \
                ONLY if you can guarantee that
the ENTIRE namespace of '' \
                supersets all the
local entries. If in doubt, it is safe to leave \
                this option disabled.

All masquerade? [N] 

As recommended, we won't enable "all masquerade".

Don't masquerade mail to local users
Send mail to local recipients without masquerading.

Daunt masquerade local? [N]

we'll also leave local masquerading disabled.

Always Add Domain
If enabled, the local host domain is included \
                even on locally delivered mail.
Normally it is not added unless it is \
                already present.

Always add domain? [N]

This means that local only e-mail will not have the machine name or domain name appended to it; this is the default behavior, and should be left as is.

Mail Acceptance
Sendmail is usually configured to accept mail \
                for your mail name
( However, under special \
                circumstances you
may not wish sendmail to do this, particularly \
                if (and disabling this option
generally requires that) mail for \
                '' is MXed
to another host. If in doubt, it is safe to \
                leave this option enabled.

Accept mail for ''? [Y]

As directed, it is safe to simply leave this option enabled.

Alternate Names
In addition to the canonical mail name \
                '', you can
add any number of additional alternate \
                names to recognize for receiving mail.
If other hosts are MXed to you for local mail, \
                this is where you should list
them. This list is saved into the file \
so it can be changed later as needed.

To answer this question, separate each \
                alternate name with a space, or answer
'NONE' to eliminate all alternate names.

Alternate names? [] 

This option is similar to the "local_domains" option in Exim; it specifies a list of domain names which we consider to be "local" to this system; ie, we will accept and attempt to deliver e-mail destined for user@domain. Sendmail keeps a list of these domains in the "/etc/mail/local-host-names" files.

Trusted Users
Sendmail allows a special group of users to \
                set their envelope "From" address
using the -f option without generating a \
                warning message. If you have
software such as Majordomo installed, you \
                will want to include the usernames
from such software here. Note that "root", \
                "daemon", and "uucp" are included
automatically and do not need to be specified. \
                This list is saved into the
file /etc/mail/trusted-users so it can be \
                changed later as needed.

To answer this question, separate each \
                username with a space, or answer
'NONE' to eliminate all usernames.

Trusted users? [] 

Leave this as the default, unless you have a specific reason to add a trusted user here. You will normally not need to do this, unless you are running mailing list software such as Majordomo.

Redirect Feature
If enabled, this feature will allow you to \
                alias old names to
<new-address>.REDIRECT, causing \
                sendmail to return mail to the sender with
an error but indicating the recipient's new address.

Enable redirect option? [N]

This is a nice option to enable if you have a large userbase with a high rate of turnover. we'll leave this option disabled for now though.

UUCP Addresses
Sendmail can be configured to be smart \
                about UUCP addresses, or it can do
nothing special with UUCP addresses at all. \
                If you care about UUCP, you will
need to do some additional configuration, \
                perhaps outside of this script.

*** NOTE *** If you use a smart host or do \
                any kind of forwarding (ie
                important that you say "Yes"
here to prevent a multi-level relay hole - \
                unless you know for *SURE* that
your smart-host does not deal with UUCP addresses.

(Be safe and just say Y)

Enable UUCP addressing? [Y] 

UUCP (Unix to Unix Copy Protocol) was the method used for transfering e-mail between Unix systems before the advent of the Internet. It is still very useful for handling e-mail for systems which do not have a permanent Internet connection. It's recommended that you leave this setting on.

Sticky Host
If enabled, mail sent to '' is \
                marked as
"sticky" -- that is, the local addresses aren't \
                matched against UDB and don't
go through ruleset 5. This is used if you want \
                a setup where 'user' is not
necessarily the same as '', \
                e.g., to make
a distinct domain-wide namespace. \
                If in doubt, it is safe to leave this
option disabled.

Enable sticky host option? [N]

As recommended, you can leave this option disabled.

If you are directly connected to the Internet and \
                have access to a domain
name server, you should enable this option.

Enable DNS? [Y]

If you are configuring a dial-up system, you can disable this option; otherwise, you should always have it enabled.

Best MX is Local
If enabled, this option will cause sendmail to accept \
                mail as though locally
addressed for any host that lists this machine as the \
                best possible MX record.
This generates additional DNS traffic, but should be \
                OK for low-to-medium
traffic hosts. N.B.: This feature is fundamentally \
                incompatible with wildcard
MX records. If you have a wildcard MX record that \
                matches your domain, you
cannot use this feature.

Assume best MX is local? [N]

We will leave this disabled for now.

If enabled, this option causes sendmail to read \
                mail routing rules from
the text file /etc/mail/mailertable.  This is needed \
                for unusual mailers like
ifmail and fax programs.
More information is in \

Enable the mailertable feature? [N]

You should peruse the documentation found in "/usr/share/doc/sendmail-doc/op/op.txt.gz" to get an idea of what you can do here; but we can leave this disabled for now.

Sendmail Restricted Shell
If enabled, this option causes sendmail to use the \
                sendmail restricted shell
program (smrsh) instead of /bin/sh for mailing to \
                programs. This improves your
ability to control what gets run via email; only \
                those programs which appear
in a special directory can be run. If you enable \
                this option, please carefully
read the smrsh(8) man page for further information.

Use the Sendmail Restricted Shell (smrsh)? [Y]

This is a desired security option for Sendmail, and should be enabled unless you have a very specific reason not to do so.

Mailer Name
You can change the name used for internally \
                generated outgoing messages.
Usually this is 'MAILER-DAEMON' but it would \
                not be unreasonable to change
it to something such as 'postmaster'.

Mailer name? [MAILER-DAEMON]

Leave this as "MAILER-DAEMON".

Me Too
Sendmail normally excludes the sender address \
                from group expansion.  Enabling
this option will cause the sender to be included.

Enable me too option? [N]

This option is self-explanatory; you can simply leave it at the default.

Message Timeouts
Sendmail will issue a warning message to the \
                sender if it can't deliver a
message within a reasonable amount of time. \
                It will also send a failure
notification and give up trying to deliver the \
                message if it can't deliver it
after an unreasonable amount of time.

You can configure the message timeouts after \
                which warning and failure
notifications are sent. Sendmail's defaults are 4 \
                hours and 5 days (4h/5d),
respectively, but many people feel warnings after \
                only 4 hours are premature.

Message timeouts? [4h/5d]

You can leave the values at the default, unless you are wanting to tweak your mail system.

Configuration Complete
Advanced configuration, such as alternate mailers, \
                the use of mailertables,
Bitnet domains, and UUCP domains can be \
                accomplished by manually editing the
/etc/mail/ configuration file and rerunning
'/usr/sbin/sendmailconfig' to generate the \
                appropriate /etc/mail/
file. (Local changes made at the end of /etc/mail/
will be preserved by '/usr/sbin/sendmailconfig'.)