Annotation of wikisrc/guide/mail.mdwn, revision 1.5
1.4 jdf 1: **Contents**
3: [[!toc levels=3]]
1.1 jdf 5: # Mail and news
1.3 jdf 7: This chapter explains how to set up NetBSD to use mail and news. Only a simple
8: but very common setup is described: the configuration of a host connected to the
9: Internet with a modem through a provider. You can think of this chapter as the
1.1 jdf 10: continuation of
1.3 jdf 11: [[Setting up TCP/IP on NetBSD in practice|guide/net-practice]], assuming a
12: similar network configuration. Even this *simple* setup proves to be difficult
13: if you don't know where to start or if you've only read introductory or
14: technical documentation. A general description of mail and news
15: configuration is beyond the scope of this guide; please read a good Unix
1.1 jdf 16: Administration book (some very good ones are listed on the NetBSD site).
1.3 jdf 18: This chapter also briefly describes the configuration (but not the usage) of two
19: popular applications, mutt for mail and tin for news. The usage is not described
20: because they are easy to use and well documented. Obviously, both mutt and tin
21: are not mandatory choices: many other similar applications exist but I think
22: that they are a good starting point because they are widely used, simple, work
23: well and don't use too much disk space and memory. Both are console mode
1.1 jdf 24: programs; if you prefer graphics applications there are also many choices for X.
1.3 jdf 26: In short, the programs required for the configuration described in this chapter
1.1 jdf 27: are:
29: * postfix
30: * fetchmail
31: * mutt
32: * tin
1.3 jdf 34: Of these, only postfix is installed with the base system; you can install the
1.1 jdf 35: other programs from the NetBSD package collection, pkgsrc.
1.3 jdf 37: *Note*: Since NetBSD 4.0, postfix is the default MTA (Mail Transport Agent) and
38: sendmail was removed. Also, because sendmail is widely popular and several
39: programs like fetchmail are designed to be used with it, postfix includes a
40: command line wrapper that accepts sendmail's commands line syntax but works with
41: postfix. See
1.1 jdf 43: for more details.
1.3 jdf 45: Before continuing, remember that none of the programs presented in this chapter
46: is mandatory: there are other applications performing similar tasks and many
47: users prefer them. You'll find different opinions reading the mailing lists. You
48: can also use different strategies for sending and receiving mail: the one
49: explained here is only a starting point; once you understand how it works you'll
50: probably want to modify it to suit your needs or to adopt a different method
1.1 jdf 51: altogether.
1.3 jdf 53: At the opposite extreme of the example presented here, there is the usage of an
54: application like Mozilla, which does everything and frees you from the need of
55: configuring many components: with Mozilla you can browse the Internet, send and
56: receive mail and read news. Besides, the setup is very simple. There is a price
57: to pay, though: Mozilla is a "closed" program that will not cooperate easily
1.1 jdf 58: with other standard Unix utilities.
1.3 jdf 60: Another possibility is to use emacs to read mail and news. Emacs needs no
61: introduction to Unix users but, in case you don't know, it is an extensible
62: editor (although calling emacs an editor is somewhat reductive) which becomes a
63: complete work environment, and can be used to read mail, news and to perform
64: many operations. For many people emacs is the only environment that they need
65: and they use it for all their work. The configuration of emacs for mail and news
1.1 jdf 66: is described in the emacs manual.
1.3 jdf 68: In the rest of this chapter we will deal with a host connected to the Internet
1.1 jdf 69: through a PPP connection via serial modem to a provider.
1.3 jdf 71: * the local host's name is `ape` and the internal network is `insetti.net`,
1.1 jdf 72: which means that the FQDN (Fully Qualified Domain Name) is `ape.insetti.net`.
73: * the user's login name on ape is `carlo`.
74: * the provider's name is BigNet.
75: * the provider's mail server is `mail.bignet.it`.
76: * the provider's news server is `news.bignet.it`.
1.3 jdf 77: * the user's (`carlo`) account at the provider is `alan` with the password
1.1 jdf 78: `pZY9o`.
80: First some basic terminology:
1.3 jdf 82: * *MUA (mail user agent)* -- a program to read and write mail. For example:
83: mutt, elm and pine but also the simple mail application installed with the
1.1 jdf 84: base system.
1.3 jdf 86: * *MTA (mail transfer agent)* -- a program that transfers mail between two host
87: but also locally (on the same host). The MTA decides the path that the mail
88: will follow to get to the destination. On other BSD systems (but not only)
89: the standard MTA is sendmail, other examples are qmail, exim and Microsoft
1.1 jdf 90: Exchange.
1.3 jdf 92: * *MDA (mail delivery agent)* -- a program, usually used by the MTA, that
93: delivers the mail; for example, it physically puts the messages in the
94: recipient's mailbox. For example, postfix uses one or more MDAs to deliver
1.1 jdf 95: mail, and procmail is another well-known MDA.
1.3 jdf 97: The following figure depicts the mail system that we want to set up. Between the
98: local network (or the single host) and the provider there is a modem PPP
99: connection. The *bubbles* with the thick border (postfix, fetchmail, mutt) are
100: the programs launched manually by the user; the remaining bubbles are the
101: programs that are launched automatically. The circled numbers refer to the
1.1 jdf 102: logical steps of the mail cycle:
104: ![Structure of the mail system](/guide/images/mail1.gif)
1.3 jdf 106: 1. In step (1) mail is downloaded from the provider's POP server using
107: fetchmail, which hands messages off to postfix's sendmail wrapper to put the
1.1 jdf 108: messages in the user's mailbox.
1.3 jdf 110: 2. In step (2) the user launches mutt (or another MUA) to read mail, reply and
1.1 jdf 111: write new messages.
1.3 jdf 113: 3. In step (3) the user *sends* the mail from within mutt. Messages are
1.1 jdf 114: accumulated in the spool area.
1.3 jdf 116: 4. In step (4) the user calls postfix's sendmail wrapper to transfer the
117: messages to the provider's SMTP server, that will deliver them to the final
118: destination (possibly through other mail servers). The provider's SMTP server
1.1 jdf 119: acts as a *relay* for our mail.
1.3 jdf 121: The connection with the provider must be up only during steps (1) and (4); for
1.1 jdf 122: the remaining steps it is not needed.
124: ## postfix
1.3 jdf 126: When an MTA must deliver a local message, it is delivered directly. If the
127: message is intended for a different domain, the MTA must find out the address of
1.1 jdf 128: the mail server for that domain. Postfix uses the DNS service (described in
1.3 jdf 129: [[The Domain Name System|guide/dns]]) to find a mail exchanger handling mail for
1.1 jdf 130: the given domain, and delivers the message to that mail server then.
1.3 jdf 132: Postfix is controlled by a set of configuration files and databases, of which
1.1 jdf 133: `/etc/postfix/main.cf` and `/etc/postfix/master.cf` are the most important.
1.3 jdf 135: *Note*: Prior to version 1.5 of NetBSD, the mail configuration files were in
136: `/etc` instead of `/etc/mail`. Since NetBSD 4.0, the `/etc/mail` directory is
137: only used to store the local aliases and the corresponding
1.1 jdf 139: database.
1.3 jdf 141: The first problem to be solved is that the local network we are dealing with is
142: an internal network, i.e. not directly accessible from the Internet. This means
143: that the names used internally have no meaning on the Internet; in short,
144: `ape.insetti.net` cannot be reached by an external host: no one will be able to
145: reply to a mail sent with this return address (many mail systems will even
146: reject the message as spam prevention as it comes from an unknown host). The
147: true address, the one visible from everybody, is assigned by the provider and,
148: therefore, it is necessary to convert the local address `email@example.com`
149: to the real address `firstname.lastname@example.org`. Postfix, if correctly configured, will
1.1 jdf 150: take care of this when it transfers the messages.
1.3 jdf 152: You'll probably also want to configure postfix in order to send the e-mails to
153: the provider's mail server, using it as a *relay*. In the configuration
154: described in this chapter, postfix does not directly contact the recipient's
155: mail server (as previously described) but relays all its mail to the provider's
1.1 jdf 156: mail server.
1.3 jdf 158: *Note*: The provider's mail server acts as a *relay*, which means that it
159: delivers mail which is not destined to its own domain, to another mail server.
1.1 jdf 160: It acts as an intermediary between two servers.
1.3 jdf 162: Since the connection with the provider is not always active, it is not necessary
163: to start postfix as a daemon in `/etc/rc.conf`: you can disable it with the line
164: `postfix=NO`. As a consequence it will be necessary to launch postfix manually
165: when you want to transfer mail to the provider. Local mail is delivered
1.1 jdf 166: correctly even if postfix is not active as a daemon.
168: Let's start configuring postfix.
170: ### Configuration of generic mapping
1.3 jdf 172: This type of configuration uses a new file `/etc/postfix/generic` which contains
1.1 jdf 173: the hostname mapping used by postfix to rewrite the internal hostnames.
175: The first step is therefore to write the mapping file:
177: email@example.com firstname.lastname@example.org
178: email@example.com firstname.lastname@example.org
179: email@example.com firstname.lastname@example.org
1.3 jdf 181: These entries will map the mail sent from the users given on the left side into
182: the globally valid email addresses given on the right, making it appear as if
1.1 jdf 183: the mail was really sent from that address.
1.3 jdf 185: For the sake of efficiency, `generic` must be transformed into a binary file
1.1 jdf 186: with the following command:
188: # postmap /etc/postfix/generic
1.3 jdf 190: Now it's time to create the prototype configuration file which we'll use to
1.1 jdf 191: create the postfix configuration file.
193: # vi /etc/postfix/main.cf
1.5 ! jdf 195: For the sake of simplicity, we'll only show the variables you need to change:
1.1 jdf 196:
197: relayhost = mail.bignet.it
198: smtp_generic_maps = hash:/etc/postfix/generic
1.3 jdf 200: This configuration tells postfix to rewrite the addresses of type
201: `ape.insetti.net` using the real names found in the `/etc/postfix/generic` file.
202: It also says that mail should be sent to the `mail.bignet.it` server. The
203: meaning of the options is described in detail in
1.1 jdf 204: [postconf(5)](http://netbsd.gw.com/cgi-bin/man-cgi?postconf+5+NetBSD-5.0.1+i386).
206: The last step is to reload the configuration. You can do that easily with:
208: # /etc/rc.d/postfix reload
209: postfix/postfix-script: refreshing the Postfix mail system
211: Now everything is ready to start sending mail.
213: ### Testing the configuration
1.3 jdf 215: Postfix is finally configured and ready to work, but before sending real mail it
216: is better to do some simple tests. First let's try sending a local e-mail with
1.1 jdf 217: the following command (postfix's sendmail wrapper):
219: $ sendmail carlo
220: Subject: test
222: Hello world
1.3 jdf 225: Please follow exactly the example above: leave a blank line after Subject: and
226: end the message with a line containing only one dot. Now you should be able to
227: read the message with your mail client and verify that the From: field has been
1.1 jdf 228: correctly rewritten.
230: From: email@example.com
232: ### Using an alternative MTA
234: Starting from version 1.4 of NetBSD sendmail is not called directly:
236: $ ls -l /usr/sbin/sendmail
237: lrwxr-xr-x 1 root wheel 21 Nov 1 01:14 /usr/sbin/sendmail@ -> /usr/sbin/mailwrapper
1.3 jdf 239: The purpose of mailwrapper is to allow the usage of an alternative MTA instead
240: of postfix (for example, sendmail). If you plan to use a different mailer I
241: suggest that you read the
243: and the
1.1 jdf 245: manpages, which are very clear.
247: ## fetchmail
1.3 jdf 249: If someone sends me mail, it is received and stored by the provider, and not
250: automatically transferred to the local hosts; therefore it is necessary to
251: download it. Fetchmail is a very popular program that downloads mail from a
252: remote mail server (using e.g. the Post Office Protocol, POP) and forwards it to
253: the local system for delivery (usually using postfix's sendmail wrapper). It is
254: powerful yet easy to use and configure: after installation, the file
255: `~/.fetchmailrc` must be created and the program is ready to run
256: (`~/.fetchmailrc` contains a password so appropriate permissions on the file are
1.1 jdf 257: required).
259: This is an example `.fetchmailrc`:
261: poll mail.bignet.it
262: protocol POP3
263: username alan there with password pZY9o is carlo here
265: mda "/usr/sbin/sendmail -oem %T"
1.3 jdf 267: The last line (`mda ...`) is used only if postfix is not active as daemon on the
268: system. Please note that the POP-mail server indicated in this file
269: (mail.bignet.it) is only used to retrieve mails, and that it is not necessary
1.1 jdf 270: the same as the mail relay used by postfix to send out mails.
1.3 jdf 272: After setting up the `.fetchmailrc` file, the following command can be used to
1.1 jdf 273: download and deliver mail to the local system:
275: $ fetchmail
277: The messages can now be read with mutt.
279: ## Reading and writing mail with mutt
1.3 jdf 281: Mutt is one of the most popular mail programs: it is *lightweight*, easy to use
282: and has lots of features. The man page mutt is very bare bones; the real
1.1 jdf 283: documentation is in `/usr/pkg/share/doc/mutt/`, in particular `manual.txt`.
1.3 jdf 285: Mutt's configuration is defined by the `~/.muttrc` file. The easiest way to
286: create it is to copy mutt's example muttrc file (usually
287: `/usr/pkg/share/examples/mutt/sample.muttrc`) to the home directory and modify
1.1 jdf 288: it. The following example shows how to achieve some results:
290: * Save a copy of sent mail.
1.3 jdf 291: * Define a directory and two files for incoming and outgoing mail saved by mutt
292: (in this example the directory is `~/Mail` and the files are `incoming` and
1.1 jdf 293: `outgoing`).
294: * Define some colors.
295: * Define an alias.
297: set copy=yes
298: set edit_headers
299: set folder="~/Mail"
300: unset force_name
301: set mbox="~/Mail/incoming"
302: set record="~/Mail/outgoing"
303: unset save_name
305: bind pager <up> previous-page
306: bind pager <down> next-page
308: color normal white black
309: color hdrdefault blue black
310: color indicator white blue
311: color markers red black
312: color quoted cyan black
313: color status white blue
314: color error red white
315: color underline yellow black
317: mono quoted standout
318: mono hdrdefault underline
319: mono indicator underline
320: mono status bold
322: alias pippo Pippo Verdi <firstname.lastname@example.org>
324: To start mutt:
326: $ mutt
1.3 jdf 328: Please note that mutt supports color, but this depends on the terminal settings.
1.1 jdf 329: Under X you can use "xterm-color", for example:
331: $ env TERM=xterm-color mutt
333: ## Strategy for receiving mail
1.3 jdf 335: This section describes a simple method for receiving and reading mail. The
336: connection to the provider is activated only for the time required to download
1.1 jdf 337: the messages; mail is then read offline.
339: 1. Activate the connection to the provider.
1.2 jdf 340: 2. Run `fetchmail`.
1.1 jdf 341: 3. Deactivate the connection.
342: 4. Read mail with mutt.
344: ## Strategy for sending mail
1.3 jdf 346: When mail has been written and *sent* with mutt, the messages must be
347: transferred to the provider with postfix. Mail is sent from mutt with the `y`
348: command, but this does not really send it; the messages are enqueued in the
349: spool area; if postfix is not active as a daemon it is necessary to start it
1.1 jdf 350: manually or the messages will remain on the hard disk. The necessary steps are:
1.3 jdf 352: 1. Write mail with mutt, send it and exit mutt. You can check if and what
353: messages are in the postfix mail queue using the
1.1 jdf 355: program.
356: 2. Activate the connection with the provider.
1.3 jdf 357: 3. If your provider requires you to do "SMTP-after-POP", i.e. it first wants to
358: make sure to know who you are before you are allowed to send mail (and no
1.1 jdf 359: spam), you need to run `fetchmail` again first.
1.3 jdf 360: 4. Write the command `/usr/sbin/postfix flush` to transfer the queued
1.1 jdf 361: messages to the provider.
362: 5. Deactivate the connection when the queue is empty.
364: ## Advanced mail tools
1.3 jdf 366: When you start using mail, you won't probably have very sophisticated
367: requirements and the already described standard configuration will satisfy all
368: your needs. But for many users the number of daily messages will increase with
369: time and a more rational organization of the mail storage will become necessary,
370: for example subdividing mail in different mail boxes organized by topic. If, for
371: example, you subscribe to a mailing list, you will likely receive many
372: messages every day and you will want to keep them separate from the rest of
373: your mail. You will soon find that you are spending too much time every day
1.1 jdf 374: repeating the same manual operations to organize your mail boxes.
1.3 jdf 376: Why repeat the same operations manually when you can have a program perform them
377: automatically for you? There are numerous tools that you can add to your mail
378: system to increase its flexibility and automatically process your messages.
1.1 jdf 379: Amongst the most known and used there are:
1.3 jdf 381: * *procmail*, an advanced mail delivery agent and general purpose mail filter
382: for local mail, which automatically processes incoming mail using user
1.1 jdf 383: defined rulesets. It integrates smoothly with sendmail/postfix.
384: * *spamassassin* or *spamprobe*, to help fight spam.
385: * *metamail*, a tool to process attachments.
386: * *formail*, a mail formatter.
1.3 jdf 388: In the remaining part of this section a sample configuration for procmail will
389: be presented for a very common case: delivering automatically to a user defined
390: mailbox all the messages coming from a mailing list. The configuration of
391: postfix will be modified in order to call procmail directly (procmail will be
392: the *local mailer* used by sendmail). and a custom configuration file for
1.1 jdf 393: procmail will be created.
1.3 jdf 395: First, procmail must be installed using the package system (`mail/procmail`),
1.1 jdf 396: `pkg_add` or `pkgin`.
1.3 jdf 398: Next, the configuration of postfix must be changed, in order to use procmail as
1.1 jdf 399: local mailer:
401: mailbox_command = /usr/pkg/bin/procmail
1.3 jdf 403: The line defines the path of the procmail program (you can see where procmail is
1.1 jdf 404: installed with the command `which procmail`).
1.3 jdf 406: The last step is the creation of the procmail configuration file, containing the
1.1 jdf 407: recipes for mail delivery.
1.3 jdf 409: Let's say that, for example, you subscribed to a mailing list on roses whose
410: address is `email@example.com` and that every message from the list contains the
1.1 jdf 411: following line in the header:
413: Delivered-To: firstname.lastname@example.org
1.3 jdf 415: Assuming you want to automatically sort all mails going over that list into the
416: local mail folder `roses_list`, the procmail configuration file (`.procmailrc`)
1.1 jdf 417: looks like this:
424: * ^Delivered-To: email@example.com
1.3 jdf 427: The previous file contains only one rule, beginning with the line containing
428: `:0`. The following line identifies all messages containing the string
429: `Delivered-To: firstname.lastname@example.org` and the last line says that the selected
430: messages must go to the `roses_list` mailbox (which you should have created in
431: $MAILDIR). The remaining messages will be delivered to the default mailbox. Note
1.1 jdf 432: that $MAILDIR is the same directory that you have configured with mutt:
434: set folder="~/Mail"
1.3 jdf 436: Of course the mailing list is only an example; procmail is a very versatile tool
437: which can be used to filter mail based on many criteria. As usual, refer to the
438: man pages for more details:
1.1 jdf 443: (this last one contains many examples of configuration files).
445: ## News with tin
1.3 jdf 447: The word *news* indicates the set of messages posted to the USENET newsgroups, a
448: service available on the Internet. Each newsgroup contains articles related to a
449: specific topic. Reading a newsgroup is different than reading a mailing list:
450: when you subscribe to a mailing list you receive the articles by mail and you
451: read them with a standard mail program like mutt, which you use also to send
452: replies. News, instead, are read directly from a news server with a dedicated
453: program called *newsreader* like, for example, tin. With tin you can subscribe
454: to the newsgroups that you're interested in and follow the *threads*. A thread
455: is a sequence of articles which all derive from an article that we could call
456: *original*. In short, a message is sent to the group, someone answers, other
457: people answer to those who answered in the first place and so on, creating a
458: tree like structure of messages and replies: without a newsreader it is
1.1 jdf 459: impossible to understand the correct sequence of messages.
1.3 jdf 461: After the installation of tin (from the package collection as usual) the only
462: thing left to do is to write the name of the NNTP server in the file
1.1 jdf 463: `/usr/pkg/etc/nntp/server`, which you may need to create first. For example:
1.3 jdf 467: Once this has been done, the program can be started with the command `tin`. On
1.1 jdf 468: the screen something similar to the following example will be displayed:
470: $ tin
471: Connecting to news.bignet.it...
472: news.bignet.it InterNetNews NNRP server INN 1.7.2 08-Dec-1997 ready (posting ok).
473: Reading groups from active file...
474: Checking for new groups...
475: Reading attributes file...
476: Reading newsgroups file...
477: Creating newsrc file...
478: Autosubscribing groups...
479: Reading newsrc file...
1.3 jdf 481: Be patient when you connect for the first time, because tin downloads an immense
482: list of newsgroups to which you can subscribe and this takes several minutes.
483: When the download is finished, the program's main screen is displayed; usually
1.1 jdf 484: no groups are displayed; to see the list of groups press `y`. To subscribe to a
485: group, move on the group's name and press `y`.
1.3 jdf 487: Once that you have subscribed to some newsgroups you can start tin more quickly
488: with the command `tin -Q`. The search for new groups is disabled (`-q`), only
489: active groups are searched (`-n`) and newsgroup description are not loaded
490: (`-d`): it will not be possible to use the `y` (yank) command in tin. When tin
1.1 jdf 491: is started with this option it can't tell if a newsgroup is moderated or not.
1.3 jdf 493: Note that if you are connecting from an internal network (like in our example),
494: when you send ("post") a message the address at the beginning of the message
495: will be wrong (because it is the internal address). To solve the problem, use
496: the option `mail_address` in the tin configuration file (`~/.tin/tinrc`) or set
1.1 jdf 497: the `REPLYTO` environment variable.
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