<center>
<img src="images/exim-blue-ld.png" alt="[big logo]">
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- <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
<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>
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+ <h4>$Cambridge$</h4>
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