Sendmail Configuration
Sendmail - Mail Transfer Agent (MTA), it is a popular, UNIX based system for implementing the simple mail transfer protocol (SMTP) for transmitting email.
To configure Sendmail , log in as admin and select Sendmail
in the System Monitor section of the left-side menu.
Sendmail Options
- Send outgoing mail via host: unless Delivery directly is chosen, sendmail will forward any outgoing mail not destined for users of your system to the given host.
- Forward unqualified usernames to host: specifies if a mail sent by a local user to an unqualified address (joesmith instead of joesmith@example.com) is to be forwarded to a local server or to another mail host specified here.
- Forward mail for local users to host: unless Deliver locally is chosen, all mail that would normally be delivered to local users will be forwarded to the specified host.
- Delivery mode: controls when messages send to this mail server are delivered.
- Background: messages are delivered as soon as possible in the background.
- Queue only: submitted messages are merely placed in the queue, and not delivered until the queue is flushed manually.
- Interactive: messages are delivered immediately.
- Deferred: like Queue only,
but no DNS or NIS lookups are done for submitted messages.
- SMTP port options: configures what IP address and port the sendmail server listens on.
- Max load average for sending:
determines the load average beyond which
outgoing messages are no longer sent, but instead queued for later delivery.
This option is useful for preventing heavy mail activity from overloading your system.
- Max load average for receiving:
determines the load average beyond which sendmail
no longer accepts incoming messages via SMTP,
forcing other mail servers to queue them for later delivery.
This option is useful for preventing heavy mail traffic from overloading your system.
- Max child processes: controls the maximum number
of child processes sendmail will start to handle incoming email.
Useful if too much memory is being used processing incoming messages.
- Max connections/second:
determines the maximum number of incoming email messages accepted per second.
Useful if incoming mail is using up too much memory or CPU time on your system.
- Min time before retrying send:
sets the minimum time a message will wait in the queue before sendmail attempts to re-send it.
This time must be given as a number followed by a character for the units, such as
30m or 1d.
Valid units are s = seconds,
m = minutes, h = hours, d = days and w = weeks.
- Maximum queue size: determines the maximum number of queued email messages that sendmail will process in one queue run.
- Time before giving up: determines the maximum number of queued email messages that sendmail will process in one queue run.
- Time before sending warning: determines time limit after which sendmail would return message to sender.
- Mail queue directory: specifies directory sendmail
uses for storing queued email messages.
- Send error messages to: determines which address sendmail
sends notifications of delivery failures to
(in addition to the person who sent the failed email).
By default it is the local address Postmaster,
which is usually aliased to root.
- User forward files:
a colon-separated list of pathnames that determines
where sendmail looks for the per-user forwarding
file when delivering email.
The variables $z for the user's home directory
and $w for the system hostname can be used in the path.
- Min free disk space:
if free disk space becomes less than the number specified,
sendmail will refuse to queue up
any incoming messages from other systems.
Useful to prevent sendmail from using up all the space
on the filesystem in which the queue directory is stored.
- Max message size: if the size of a message exceeds this value,
the message will be bounced by sendmail.
- Log level: determines the amount of
information sendmail writes to its log file via syslog.
- MIME-encode bounce messages? determines whether
bounce messages should be send in multi-part MIME format,
or as a simple plain text message.
Use the latter option if you have lots of users
running clients that cannot handle MIME.
-
Accept mail for users' real names?
Enable this option to be able to send messages for both users' login names
in the system (like jsmith@example.com) and their real names
(like Joe.Smith@example.com).
-
Maximum mail hop count:
determines the maximum number of mail servers
sendmail will allow a message to pass through before rejecting it.
-
File security options:
this option allows to turn off
checking of support files
that are by default checked by Sendmail for security reasons.
However, it is strongly suggested
It is strongly suggested that you solve possible problems with permissions,
rather than turning off any of these checks.
Make sure to click Save and Apply to preserve changes.
For more details on
sendmail configuration,
please refer to Sendmail documentation.
Mail Aliases
Aliases - format of the Sendmail alias database. The aliases file provides a system-wide mechanism to redirect mail for local recipients.
The form to create aliase:
To edit the existent aliases, click on the user's name in the list, and you will see the form similar to the form to create aliases. Each time you edit a user account, you may add a new Alias To field:
- Address: an address to be aliased must not include its domain name, it
must be jsmith instead of jsmith@example.com.
- Enabled: determines if this alias is currently enabled. Disabled aliases are ignored when processing incoming email.
- Alias To:
each alias may redirect mail to several recipients, and each recipient
may be one of the following:
- Email Address - a full email address (with domain name) or
local address (without domain name)
- Addresses in File - pathname to the file with the list of addresses
one per line.
- Write to File - email will be written to the specified file.
To have all email to some address thrown away,
give /dev/null as the filename.
- Feed to Program- pathname to a program that starts each time
an email message comes from this address and takes the message as
its standard input.
- Autoreply From File -
simply sends a mail automatically back to the sender
containing whatever is in the file listed in the text field.
Make sure to click Save to preserve changes.
Local Domains
Apart from mail to test.local, sendmail will only accept for local delivery mail for domains and hostnames listed in the text box. If you want your mail server to handle multiple email domains, they must all be listed on this form:
Make sure to click Save to preserve changes.
Domain Masquerading
If a domain is given above, sendmail will alter the From address of all outgoing messages to appear to come from that domain. More ....
Make sure to click Save to preserve changes.
Trusted Users
If a local user tries to send email, sendmail will only allow the user to provide a different From: address if the user is on the list to the left.
By default, sendmail doesn't allow a user
to claim to be a different user.
This is done to safeguard the system against spoofed email addresses.
However, if users they are listed among trusted users, one per line,
they will be trusted to claim they are another user or
from another domain.
Make sure to click Save to preserve changes.
Address Mappings
A domain-specific form of aliasing, allowing multiple virtual domains to be hosted on one machine. For example, if the virtuser table contained
info@foo.com - foo-info,
info@bar.com - bar-info,
then mail addressed to info@foo.com will be sent to the address foo-info, mail addressed to info@bar.com will be delivered to bar-info:
There is the address mapping list bellow. To edit already existed address mapping, click on the
address in the list, and you will see the form similar to the form to create mapping. Also you can manually edit the Sendmail file /etc/mail/virtusertable - to do it, click Manually edit /etc/mail/virtusertable.
Domain Routing
This option can be used to override routing for particular domains (which are not local host names):
Outgoing Addresses
This feature will cause unqualified addresses (i.e., without a domain) and addresses with a domain listed in class {G}-GENERICS_DOMAIN to be looked up in a map and turned into another ("generic") form, which can change both the domain name and the user name.
Outgoing Domains
Apart from mail sent by local users, sendmail will only perform outgoing address mapping for mail from hosts or domains listed in the text box.
Thus for an outgoing address entry to work the domain in the from address must be included in this list.
Make sure to click Save to preserve changes.
Domain Mapping
This option can be used to provide domain name mapping. Use of this should really be limited to your own domains. It may be useful if you change names (e.g., your company changes names from oldname.com to newname.com).If your sendmail configuration does not have the domain mapping (domaintable) feature enabled, click here to setup sendmail features.
Spam Controls
Turns on the access database feature. This option gives you the ability to allow or refuse to accept mail from specified domains for administrative reasons. Moreover, it can control the behavior of sendmail in various situations. If you need to set the antispam rules, choose Spam Controls from Sendmail Configuration page:
Sendmail's spam control feature allows to prevent spam from reaching your users by rejecting mail from certain addresses, and to prevent spammers from using your system to relay mail. By default sendmail will accept mail from any address for a local user, but prevent any client or mail server from relaying mail through your system.
To edit already set antispam rule for some source, click the mail source name from the list. Also you can manually edit /etc/mail/access - just click Manually edit /etc/mail/access button.
Relay Domains
Unless allowed by the spam control rules, sendmail will only permit relaying to domains listed in the text box below. Incoming mail messages that are not for a local user and not for one of the listed domains will be rejected. To specify domains to which relaying is allowed, click the Relay Domains icon on Sendmail Configuration page.
Make sure to click Save to preserve changes.
Sendmail M4 Configuration
Sendmail uses the M4 macro processor to ``compile'' the configuration files. More ....
This page lists the relevant entries from the Sendmail M4 configuration file /etc/mail/sendmail.mc, from which the actual configuration file /etc/mail/sendmail.cf is built.
To edit configuration entry, click one of the item in Entry type column and fill the M4 configuration entry details form.
Mail Queue
Normally, sendmail delivers messages in background mode.
However, if delivery mode is set to queue, mail is stored into queue that is
flushed by means of an outer program.
- Click on a message ID in the list to view its headers and text.
- To delete messages from the list, check corresponding boxes on the left
(or press the Select All button to select all messages), and press
Delete selected messages. Checking the box Even if locked
will forcefully delete locked messages.
User Mailboxes
Click the User Mailboxes icon and you will see the page, that contains the user mailboxes list:
To get access to mails in these mailboxes, just click one of mailboxes names in this list.
To read mail in some file enter the name to this file or click the "..." button and find it in the pop-up window.
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Admin Guide