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- <img src="images/eximX.png" alt="[big logo]">
+ <img src="images/exim-blue-ld.png" alt="[big logo]">
</center>
- <h1>Introduction to exim</h1>
+ <h1>Introduction to exim</h1>
<p>Exim is a message transfer agent (<b>MTA</b>) developed at the
University of Cambridge for use on Unix systems connected to the
set of documentation included in the exim specification,
additionally there are documents on the filtering functionality
and other documentation is being made available on this web site.
- <a href="exim-html-3.10/doc/html/oview.html">The full overview is also
+ <a href="exim-html-3.20/doc/html/oview.html">The full overview is also
available</a>.</p>
<h2>Basic Features</h2>
<ul>
<li>
- Many configuration options can be given as expansion strings,
- and as these can include file lookups, much of Exim's
- operation can be made table-driven if desired. For example,
- it is possible to do local delivery on a machine on which the
- users do not have accounts.
+ Many configuration options can be given as expansion strings,
+ and as these can include file lookups, much of Exim's
+ operation can be made table-driven if desired. For example,
+ it is possible to do local delivery on a machine on which the
+ users do not have accounts.
</li>
<!-- -->
<li>
- Regular expressions are available in a number of configuration
- parameters.
+ Regular expressions are available in a number of configuration
+ parameters.
</li>
<!-- -->
<li>
- Domain lists can include file lookups, making it possible to
- support a large number of local domains.
+ Domain lists can include file lookups, making it possible to
+ support a large number of local domains.
</li>
<!-- -->
<li>
- The maximum size of message can be specified.
+ The maximum size of message can be specified.
</li>
<!-- -->
<li>
- Exim can handle a number of independent local domains on the
- same machine; each domain can have its own alias files,
- etc. These are commonly called <b>virtual domains</b>.
+ Exim can handle a number of independent local domains on the
+ same machine; each domain can have its own alias files,
+ etc. These are commonly called <b>virtual domains</b>.
</li>
<!-- -->
<li>
- Exim contains an optional built-in mail filtering
- facility. This enables users to set up their own mail
- filtering in a straightforward manner without the need to run
- an external program. There can also be a system filter file
- that applies to all messages.
+ Exim contains an optional built-in mail filtering
+ facility. This enables users to set up their own mail
+ filtering in a straightforward manner without the need to run
+ an external program. There can also be a system filter file
+ that applies to all messages.
</li>
<!-- -->
<li>
- Periodic warnings are automatically sent to messages' senders
- when delivery is delayed -- the time between warnings is
- configurable.
+ Periodic warnings are automatically sent to messages' senders
+ when delivery is delayed -- the time between warnings is
+ configurable.
</li>
<!-- -->
<li>
- A queue run can be manually started to deliver just a
- particular portion of the queue, or those messages with a
- recipient whose address contains a given string.
+ A queue run can be manually started to deliver just a
+ particular portion of the queue, or those messages with a
+ recipient whose address contains a given string.
</li>
<!-- -->
<li>
- Exim can be configured to run as root all the time, except
- when performing local deliveries, which it always does in a
- separate process under an appropriate uid and
- gid. Alternatively, it can be configured to run as root only
- when needed; in particular, it need not run as root when
- receiving incoming messages or when sending out messages over
- SMTP.
+ Exim can be configured to run as root all the time, except
+ when performing local deliveries, which it always does in a
+ separate process under an appropriate uid and
+ gid. Alternatively, it can be configured to run as root only
+ when needed; in particular, it need not run as root when
+ receiving incoming messages or when sending out messages over
+ SMTP.
</li>
<!-- -->
</ul>
<h2>Incoming SMTP</h2>
<ul>
<li>
- SMTP calls from specific machines, optionally from specific
- idents, can be locked out, and incoming SMTP messages from
- specific senders can also be locked out.
+ SMTP calls from specific machines, optionally from specific
+ idents, can be locked out, and incoming SMTP messages from
+ specific senders can also be locked out.
</li>
<!-- -->
<li>
- Messages on the queue can be `frozen' and `thawed' by the
- administrator.
+ Messages on the queue can be `frozen' and `thawed' by the
+ administrator.
</li>
<!-- -->
</ul>
<h2>Outgoing SMTP</h2>
<ul>
<li>
- Exim can perform multiple deliveries down the same SMTP
- channel after deliveries to a host have been delayed.
+ Exim can perform multiple deliveries down the same SMTP
+ channel after deliveries to a host have been delayed.
</li>
<!-- -->
<li>
- Exim can be configured to do local deliveries immediately but
- to leave remote deliveries until the message is picked up by a
- queue-runner process. This increases the likelihood of
- multiple messages being sent down a single SMTP connection.
+ Exim can be configured to do local deliveries immediately but
+ to leave remote deliveries until the message is picked up by a
+ queue-runner process. This increases the likelihood of
+ multiple messages being sent down a single SMTP connection.
</li>
<!-- -->
<li>
- When copies of a message have to be delivered to more than one
- remote host, up to a configured maximum number of remote
- deliveries can be done in parallel.
+ When copies of a message have to be delivered to more than one
+ remote host, up to a configured maximum number of remote
+ deliveries can be done in parallel.
</li>
<!-- -->
</ul>
<h2>Local Deliveries</h2>
<ul>
<li>
- Exim stats a user's home directory before looking for a
- `<tt>.forward</tt>' file, in order to detect the case of a
- missing NFS mount.
+ Exim stats a user's home directory before looking for a
+ `<tt>.forward</tt>' file, in order to detect the case of a
+ missing NFS mount.
</li>
<!-- -->
<li>
- There is support for multiple user mailboxes controlled by
- prefixes or suffixes on the user name, either via the
- <i>filter</i> mechanism or through multiple
- `<tt>.forward</tt>' files.
+ There is support for multiple user mailboxes controlled by
+ prefixes or suffixes on the user name, either via the
+ <i>filter</i> mechanism or through multiple
+ `<tt>.forward</tt>' files.
</li>
<!-- -->
</ul>
<h2>Monitoring and Performance Tools</h2>
<ul>
<li>
- The Exim Monitor is an optional extra; it displays information
- about Exim's processing in an X window, and an administrator
- can perform a number of control actions from the window
- interface.
+ The Exim Monitor is an optional extra; it displays information
+ about Exim's processing in an X window, and an administrator
+ can perform a number of control actions from the window
+ interface.
</li>
<!-- -->
<li>
- There are a set of tools for summarising the queue, determining
- what each exim process is currently doing, examining the
- deliveries hints databases, and summarising the log files into
- a concise report on activity.
+ There are a set of tools for summarising the queue, determining
+ what each exim process is currently doing, examining the
+ deliveries hints databases, and summarising the log files into
+ a concise report on activity.
</li>
<!-- -->
</ul>
<h2>SPAM/UCE/UBE Limitation Features</h2>
<ul>
<li>
- Senders can be blocked using a variety of methods, including
- the ability to apply a set of username or regular expression
- patterns to incoming mail from particular (or all) domains.
+ Senders can be blocked using a variety of methods, including
+ the ability to apply a set of username or regular expression
+ patterns to incoming mail from particular (or all) domains.
</li>
<!-- -->
<li>
- All addresses can be checked for validity during the SMTP
- transaction thus allowing the elimination of mail from
- non-existent domains.
+ All addresses can be checked for validity during the SMTP
+ transaction thus allowing the elimination of mail from
+ non-existent domains.
</li>
<!-- -->
<li>
- Relaying can be tightly controlled based on sending host,
- network or sending/recipient domains.
+ Relaying can be tightly controlled based on sending host,
+ network or sending/recipient domains.
</li>
<!-- -->
<li>
- If all else fails the system filter can be used to deal with
- messages based on arbitrary conditions that you can program in
- (for example block mail with a particular <tt>X-Mailer:</tt>
- header.
+ If all else fails the system filter can be used to deal with
+ messages based on arbitrary conditions that you can program in
+ (for example block mail with a particular <tt>X-Mailer:</tt>
+ header.
</li>
</ul>
<h2>Limitations</h2>
<ul>
<li>
- Exim is written in ANSI C. This should not be much of a
- limitation these days. However, to help with systems that
- lack a true ANSI C library, Exim avoids making any use of the
- value returned by the `<tt>sprintf()</tt>' function, which is
- one of the main incompatibilities. It has its own version of
- `<tt>strerror()</tt>' for use with <b>SunOS4</b> and any other
- system that lacks this function, and a macro can be defined to
- turn `<tt>memmove()</tt>' into `<tt>bcopy()</tt>' if
- necessary.
+ Exim is written in ANSI C. This should not be much of a
+ limitation these days. However, to help with systems that
+ lack a true ANSI C library, Exim avoids making any use of the
+ value returned by the `<tt>sprintf()</tt>' function, which is
+ one of the main incompatibilities. It has its own version of
+ `<tt>strerror()</tt>' for use with <b>SunOS4</b> and any other
+ system that lacks this function, and a macro can be defined to
+ turn `<tt>memmove()</tt>' into `<tt>bcopy()</tt>' if
+ necessary.
</li>
<!-- -->
<li>
- Exim uses file names that are longer than 14 characters.
- </li>
+ Exim uses file names that are longer than 14 characters.
+ </li>
<!-- -->
<li>
- Exim is intended for use as an Internet mailer, and therefore
- handles addresses in RFC 822 domain format only. It cannot
- handle <i>bang paths</i>, though simple two-component bang
- paths can be converted by a straightforward rewriting
- configuration.
+ Exim is intended for use as an Internet mailer, and therefore
+ handles addresses in RFC 822 domain format only. It cannot
+ handle <i>bang paths</i>, though simple two-component bang
+ paths can be converted by a straightforward rewriting
+ configuration.
</li>
<!-- -->
<li>
- Exim insists that every address it handles has a domain
- attached. For incoming local messages, domainless addresses
- are automatically qualified with a configured domain
- value. Configuration options specify from which remote systems
- unqualified addresses are acceptable.
+ Exim insists that every address it handles has a domain
+ attached. For incoming local messages, domainless addresses
+ are automatically qualified with a configured domain
+ value. Configuration options specify from which remote systems
+ unqualified addresses are acceptable.
</li>
<!-- -->
<li>
- The only external transport currently implemented is an SMTP
- transport over a TCP/IP network (using sockets), suitable for
- machines on the Internet. However, a pipe transport is
- available, and there are facilities for writing messages to
- files in `batched SMTP' format; this can be used to send
- messages to some other transport mechanism. Batched SMTP input
- is also catered for.
+ The only external transport currently implemented is an SMTP
+ transport over a TCP/IP network (using sockets), suitable for
+ machines on the Internet. However, a pipe transport is
+ available, and there are facilities for writing messages to
+ files in `batched SMTP' format; this can be used to send
+ messages to some other transport mechanism. Batched SMTP input
+ is also catered for.
</li>
<!-- -->
</ul>
<hr>
<address><a href="mailto:Postmaster@exim.org">Nigel Metheringham</a></address>
<!-- Created: Mon Aug 25 13:21:52 BST 1997 -->
- <h4>$Id: intro.html,v 1.4 2000/04/09 22:02:33 nigel Exp $</h4>
+ <h4>$Cambridge$</h4>
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