Annotation of wikisrc/guide/mail.mdwn, revision 1.2

1.1       jdf         1: # Mail and news
                      3: This chapter explains how to set up NetBSD to use mail and news. Only a simple 
                      4: but very common setup is described: the configuration of a host connected to the 
                      5: Internet with a modem through a provider. You can think of this chapter as the 
                      6: continuation of
                      7: [[Setting up TCP/IP on NetBSD in practice|guide/net-practice]], assuming a 
                      8: similar network configuration. Even this *simple* setup proves to be difficult 
                      9: if you don't know where to start or if you've only read introductory or 
                     10: technical documentation. A general description of mail and news 
                     11: configuration is beyond the scope of this guide; please read a good Unix 
                     12: Administration book (some very good ones are listed on the NetBSD site).
                     14: This chapter also briefly describes the configuration (but not the usage) of two 
                     15: popular applications, mutt for mail and tin for news. The usage is not described 
                     16: because they are easy to use and well documented. Obviously, both mutt and tin 
                     17: are not mandatory choices: many other similar applications exist but I think 
                     18: that they are a good starting point because they are widely used, simple, work 
                     19: well and don't use too much disk space and memory. Both are console mode 
                     20: programs; if you prefer graphics applications there are also many choices for X.
                     22: In short, the programs required for the configuration described in this chapter 
                     23: are:
                     25:  * postfix
                     26:  * fetchmail
                     27:  * mutt
                     28:  * tin
                     30: Of these, only postfix is installed with the base system; you can install the 
                     31: other programs from the NetBSD package collection, pkgsrc.
                     33: *Note*: Since NetBSD 4.0, postfix is the default MTA (Mail Transport Agent) and 
                     34: sendmail was removed. Also, because sendmail is widely popular and several 
                     35: programs like fetchmail are designed to be used with it, postfix includes a 
                     36: command line wrapper that accepts sendmail's commands line syntax but works with 
                     37: postfix. See 
                     38: [sendmail(1)]( 
                     39: for more details.
                     41: Before continuing, remember that none of the programs presented in this chapter 
                     42: is mandatory: there are other applications performing similar tasks and many 
                     43: users prefer them. You'll find different opinions reading the mailing lists. You 
                     44: can also use different strategies for sending and receiving mail: the one 
                     45: explained here is only a starting point; once you understand how it works you'll 
                     46: probably want to modify it to suit your needs or to adopt a different method 
                     47: altogether.
                     49: At the opposite extreme of the example presented here, there is the usage of an 
                     50: application like Mozilla, which does everything and frees you from the need of 
                     51: configuring many components: with Mozilla you can browse the Internet, send and 
                     52: receive mail and read news. Besides, the setup is very simple. There is a price 
                     53: to pay, though: Mozilla is a "closed" program that will not cooperate easily 
                     54: with other standard Unix utilities.
                     56: Another possibility is to use emacs to read mail and news. Emacs needs no 
                     57: introduction to Unix users but, in case you don't know, it is an extensible 
                     58: editor (although calling emacs an editor is somewhat reductive) which becomes a 
                     59: complete work environment, and can be used to read mail, news and to perform 
                     60: many operations. For many people emacs is the only environment that they need 
                     61: and they use it for all their work. The configuration of emacs for mail and news 
                     62: is described in the emacs manual.
                     64: In the rest of this chapter we will deal with a host connected to the Internet 
                     65: through a PPP connection via serial modem to a provider.
                     67:  * the local host's name is `ape` and the internal network is ``, 
                     68:    which means that the FQDN (Fully Qualified Domain Name) is ``.
                     69:  * the user's login name on ape is `carlo`.
                     70:  * the provider's name is BigNet.
                     71:  * the provider's mail server is ``.
                     72:  * the provider's news server is ``.
                     73:  * the user's (`carlo`) account at the provider is `alan` with the password 
                     74:    `pZY9o`.
                     76: First some basic terminology:
                     78:  * *MUA (mail user agent)* -- a program to read and write mail. For example: 
                     79:    mutt, elm and pine but also the simple mail application installed with the 
                     80:    base system.
                     82:  * *MTA (mail transfer agent)* -- a program that transfers mail between two host 
                     83:    but also locally (on the same host). The MTA decides the path that the mail 
                     84:    will follow to get to the destination. On other BSD systems (but not only) 
                     85:    the standard MTA is sendmail, other examples are qmail, exim and Microsoft 
                     86:    Exchange.
                     88:  * *MDA (mail delivery agent)* -- a program, usually used by the MTA, that 
                     89:    delivers the mail; for example, it physically puts the messages in the 
                     90:    recipient's mailbox. For example, postfix uses one or more MDAs to deliver 
                     91:    mail, and procmail is another well-known MDA.
                     93: The following figure depicts the mail system that we want to set up. Between the 
                     94: local network (or the single host) and the provider there is a modem PPP 
                     95: connection. The *bubbles* with the thick border (postfix, fetchmail, mutt) are 
                     96: the programs launched manually by the user; the remaining bubbles are the 
                     97: programs that are launched automatically. The circled numbers refer to the 
                     98: logical steps of the mail cycle:
                    100: ![Structure of the mail system](/guide/images/mail1.gif)
                    102:  1. In step (1) mail is downloaded from the provider's POP server using 
                    103:     fetchmail, which hands messages off to postfix's sendmail wrapper to put the 
                    104:     messages in the user's mailbox.
                    106:  2. In step (2) the user launches mutt (or another MUA) to read mail, reply and 
                    107:     write new messages.
                    109:  3. In step (3) the user *sends* the mail from within mutt. Messages are 
                    110:     accumulated in the spool area.
                    112:  4. In step (4) the user calls postfix's sendmail wrapper to transfer the 
                    113:     messages to the provider's SMTP server, that will deliver them to the final 
                    114:     destination (possibly through other mail servers). The provider's SMTP server 
                    115:     acts as a *relay* for our mail.
                    117: The connection with the provider must be up only during steps (1) and (4); for 
                    118: the remaining steps it is not needed.
                    120: ## postfix
                    122: When an MTA must deliver a local message, it is delivered directly. If the 
                    123: message is intended for a different domain, the MTA must find out the address of 
                    124: the mail server for that domain. Postfix uses the DNS service (described in
                    125: [[The Domain Name System|guide/dns]]) to find a mail exchanger handling mail for 
                    126: the given domain, and delivers the message to that mail server then.
                    128: Postfix is controlled by a set of configuration files and databases, of which 
                    129: `/etc/postfix/` and `/etc/postfix/` are the most important.
                    131: *Note*: Prior to version 1.5 of NetBSD, the mail configuration files were in 
                    132: `/etc` instead of `/etc/mail`. Since NetBSD 4.0, the `/etc/mail` directory is 
                    133: only used to store the local aliases and the corresponding 
                    134: [postmap(1)]( 
                    135: database.
                    137: The first problem to be solved is that the local network we are dealing with is 
                    138: an internal network, i.e. not directly accessible from the Internet. This means 
                    139: that the names used internally have no meaning on the Internet; in short, 
                    140: `` cannot be reached by an external host: no one will be able to 
                    141: reply to a mail sent with this return address (many mail systems will even 
                    142: reject the message as spam prevention as it comes from an unknown host). The 
                    143: true address, the one visible from everybody, is assigned by the provider and, 
                    144: therefore, it is necessary to convert the local address `` 
                    145: to the real address ``. Postfix, if correctly configured, will 
                    146: take care of this when it transfers the messages.
                    148: You'll probably also want to configure postfix in order to send the e-mails to 
                    149: the provider's mail server, using it as a *relay*. In the configuration 
                    150: described in this chapter, postfix does not directly contact the recipient's 
                    151: mail server (as previously described) but relays all its mail to the provider's 
                    152: mail server.
                    154: *Note*: The provider's mail server acts as a *relay*, which means that it 
                    155: delivers mail which is not destined to its own domain, to another mail server. 
                    156: It acts as an intermediary between two servers.
                    158: Since the connection with the provider is not always active, it is not necessary 
                    159: to start postfix as a daemon in `/etc/rc.conf`: you can disable it with the line 
                    160: `postfix=NO`. As a consequence it will be necessary to launch postfix manually 
                    161: when you want to transfer mail to the provider. Local mail is delivered 
                    162: correctly even if postfix is not active as a daemon.
                    164: Let's start configuring postfix.
                    166: ### Configuration of generic mapping
                    168: This type of configuration uses a new file `/etc/postfix/generic` which contains 
                    169: the hostname mapping used by postfix to rewrite the internal hostnames.
                    171: The first step is therefore to write the mapping file:
                    177: These entries will map the mail sent from the users given on the left side into 
                    178: the globally valid email addresses given on the right, making it appear as if 
                    179: the mail was really sent from that address.
                    181: For the sake of efficiency, `generic` must be transformed into a binary file 
                    182: with the following command:
                    184:     # postmap /etc/postfix/generic
                    186: Now it's time to create the prototype configuration file which we'll use to 
                    187: create the postfix configuration file.
                    189:     # vi /etc/postfix/
                    191: For the sake of simplicity, we'll only show the variables you need change:
                    193:     relayhost =
                    194:     smtp_generic_maps = hash:/etc/postfix/generic
                    196: This configuration tells postfix to rewrite the addresses of type 
                    197: `` using the real names found in the `/etc/postfix/generic` file. 
                    198: It also says that mail should be sent to the `` server. The 
                    199: meaning of the options is described in detail in 
                    200: [postconf(5)](
                    202: The last step is to reload the configuration. You can do that easily with:
                    204:     # /etc/rc.d/postfix reload
                    205:     postfix/postfix-script: refreshing the Postfix mail system
                    207: Now everything is ready to start sending mail.
                    209: ### Testing the configuration
                    211: Postfix is finally configured and ready to work, but before sending real mail it 
                    212: is better to do some simple tests. First let's try sending a local e-mail with 
                    213: the following command (postfix's sendmail wrapper):
                    215:     $ sendmail carlo
                    216:     Subject: test
                    218:     Hello world
                    219:     .
                    221: Please follow exactly the example above: leave a blank line after Subject: and 
                    222: end the message with a line containing only one dot. Now you should be able to 
                    223: read the message with your mail client and verify that the From: field has been 
                    224: correctly rewritten.
                    226:     From:
                    228: ### Using an alternative MTA
                    230: Starting from version 1.4 of NetBSD sendmail is not called directly:
                    232:     $ ls -l /usr/sbin/sendmail
                    233:     lrwxr-xr-x  1 root  wheel  21 Nov  1 01:14 /usr/sbin/sendmail@ -> /usr/sbin/mailwrapper
                    235: The purpose of mailwrapper is to allow the usage of an alternative MTA instead 
                    236: of postfix (for example, sendmail). If you plan to use a different mailer I 
                    237: suggest that you read the 
                    238: [mailwrapper(8)]( 
                    239: and the 
                    240: [mailer.conf(5)]( 
                    241: manpages, which are very clear.
                    243: ## fetchmail
                    245: If someone sends me mail, it is received and stored by the provider, and not 
                    246: automatically transferred to the local hosts; therefore it is necessary to 
                    247: download it. Fetchmail is a very popular program that downloads mail from a 
                    248: remote mail server (using e.g. the Post Office Protocol, POP) and forwards it to 
                    249: the local system for delivery (usually using postfix's sendmail wrapper). It is 
                    250: powerful yet easy to use and configure: after installation, the file 
                    251: `~/.fetchmailrc` must be created and the program is ready to run 
                    252: (`~/.fetchmailrc` contains a password so appropriate permissions on the file are 
                    253: required).
                    255: This is an example `.fetchmailrc`:
                    257:     poll
                    258:     protocol POP3
                    259:     username alan there with password pZY9o is carlo here
                    260:     flush
                    261:     mda "/usr/sbin/sendmail -oem %T"
                    263: The last line (`mda ...`) is used only if postfix is not active as daemon on the 
                    264: system. Please note that the POP-mail server indicated in this file 
                    265: ( is only used to retrieve mails, and that it is not necessary 
                    266: the same as the mail relay used by postfix to send out mails.
                    268: After setting up the `.fetchmailrc` file, the following command can be used to 
                    269: download and deliver mail to the local system:
                    271:     $ fetchmail
                    273: The messages can now be read with mutt.
                    275: ## Reading and writing mail with mutt
                    277: Mutt is one of the most popular mail programs: it is *lightweight*, easy to use 
                    278: and has lots of features. The man page mutt is very bare bones; the real 
                    279: documentation is in `/usr/pkg/share/doc/mutt/`, in particular `manual.txt`.
                    281: Mutt's configuration is defined by the `~/.muttrc` file. The easiest way to 
                    282: create it is to copy mutt's example muttrc file (usually 
                    283: `/usr/pkg/share/examples/mutt/sample.muttrc`) to the home directory and modify 
                    284: it. The following example shows how to achieve some results:
                    286:  * Save a copy of sent mail.
                    287:  * Define a directory and two files for incoming and outgoing mail saved by mutt 
                    288:    (in this example the directory is `~/Mail` and the files are `incoming` and 
                    289:    `outgoing`).
                    290:  * Define some colors.
                    291:  * Define an alias.
                    293:     set copy=yes
                    294:     set edit_headers
                    295:     set folder="~/Mail"
                    296:     unset force_name
                    297:     set mbox="~/Mail/incoming"
                    298:     set record="~/Mail/outgoing"
                    299:     unset save_name
                    301:     bind pager <up> previous-page
                    302:     bind pager <down> next-page
                    304:     color normal white black
                    305:     color hdrdefault blue black
                    306:     color indicator white blue
                    307:     color markers red black
                    308:     color quoted cyan black
                    309:     color status white blue
                    310:     color error red white
                    311:     color underline yellow black
                    313:     mono quoted standout
                    314:     mono hdrdefault underline
                    315:     mono indicator underline
                    316:     mono status bold
                    318:     alias pippo Pippo Verdi <>
                    320: To start mutt:
                    322:     $ mutt
                    324: Please note that mutt supports color, but this depends on the terminal settings. 
                    325: Under X you can use "xterm-color", for example:
                    327:     $ env TERM=xterm-color mutt
                    329: ## Strategy for receiving mail
                    331: This section describes a simple method for receiving and reading mail. The 
                    332: connection to the provider is activated only for the time required to download 
                    333: the messages; mail is then read offline.
                    335:  1. Activate the connection to the provider.
1.2     ! jdf       336:  2. Run `fetchmail`.
1.1       jdf       337:  3. Deactivate the connection.
                    338:  4. Read mail with mutt.
                    340: ## Strategy for sending mail
                    342: When mail has been written and *sent* with mutt, the messages must be 
                    343: transferred to the provider with postfix. Mail is sent from mutt with the `y` 
                    344: command, but this does not really send it; the messages are enqueued in the 
                    345: spool area; if postfix is not active as a daemon it is necessary to start it 
                    346: manually or the messages will remain on the hard disk. The necessary steps are:
                    348:  1. Write mail with mutt, send it and exit mutt. You can check if and what 
                    349:     messages are in the postfix mail queue using the 
                    350:     [mailq(1)]( 
                    351:     program.
                    352:  2. Activate the connection with the provider.
                    353:  3. If your provider requires you to do "SMTP-after-POP", i.e. it first wants to 
                    354:     make sure to know who you are before you are allowed to send mail (and no 
                    355:     spam), you need to run `fetchmail` again first.
                    356:  4. Write the command `/usr/sbin/postfix flush` to transfer the queued 
                    357:     messages to the provider.
                    358:  5. Deactivate the connection when the queue is empty.
                    360: ## Advanced mail tools
                    362: When you start using mail, you won't probably have very sophisticated 
                    363: requirements and the already described standard configuration will satisfy all 
                    364: your needs. But for many users the number of daily messages will increase with 
                    365: time and a more rational organization of the mail storage will become necessary, 
                    366: for example subdividing mail in different mail boxes organized by topic. If, for 
                    367: example, you subscribe to a mailing list, you will likely receive many 
                    368: messages every day and you will want to keep them separate from the rest of 
                    369: your mail. You will soon find that you are spending too much time every day 
                    370: repeating the same manual operations to organize your mail boxes.
                    372: Why repeat the same operations manually when you can have a program perform them 
                    373: automatically for you? There are numerous tools that you can add to your mail 
                    374: system to increase its flexibility and automatically process your messages. 
                    375: Amongst the most known and used there are:
                    377:  * *procmail*, an advanced mail delivery agent and general purpose mail filter 
                    378:    for local mail, which automatically processes incoming mail using user 
                    379:    defined rulesets. It integrates smoothly with sendmail/postfix.
                    380:  * *spamassassin* or *spamprobe*, to help fight spam.
                    381:  * *metamail*, a tool to process attachments.
                    382:  * *formail*, a mail formatter.
                    384: In the remaining part of this section a sample configuration for procmail will 
                    385: be presented for a very common case: delivering automatically to a user defined 
                    386: mailbox all the messages coming from a mailing list. The configuration of 
                    387: postfix will be modified in order to call procmail directly (procmail will be 
                    388: the *local mailer* used by sendmail). and a custom configuration file for 
                    389: procmail will be created.
                    391: First, procmail must be installed using the package system (`mail/procmail`), 
                    392: `pkg_add` or `pkgin`.
                    394: Next, the configuration of postfix must be changed, in order to use procmail as 
                    395: local mailer:
                    397:     mailbox_command = /usr/pkg/bin/procmail
                    399: The line defines the path of the procmail program (you can see where procmail is 
                    400: installed with the command `which procmail`).
                    402: The last step is the creation of the procmail configuration file, containing the 
                    403: recipes for mail delivery.
                    405: Let's say that, for example, you subscribed to a mailing list on roses whose 
                    406: address is `` and that every message from the list contains the 
                    407: following line in the header:
                    409:     Delivered-To:
                    411: Assuming you want to automatically sort all mails going over that list into the 
                    412: local mail folder `roses_list`, the procmail configuration file (`.procmailrc`) 
                    413: looks like this:
                    415:     PATH=/bin:/usr/bin:/usr/pkg/bin
                    416:     MAILDIR=$HOME/Mail
                    417:     LOGFILE=$MAILDIR/from
                    419:     :0
                    420:     * ^Delivered-To:
                    421:     roses_list
                    423: The previous file contains only one rule, beginning with the line containing 
                    424: `:0`. The following line identifies all messages containing the string 
                    425: `Delivered-To:` and the last line says that the selected 
                    426: messages must go to the `roses_list` mailbox (which you should have created in 
                    427: $MAILDIR). The remaining messages will be delivered to the default mailbox. Note 
                    428: that $MAILDIR is the same directory that you have configured with mutt:
                    430:     set folder="~/Mail"
                    432: Of course the mailing list is only an example; procmail is a very versatile tool 
                    433: which can be used to filter mail based on many criteria. As usual, refer to the 
                    434: man pages for more details: 
                    435: [procmail(1)](, 
                    436: [procmailrc(5)](, 
                    437: and 
                    438: [procmailex(5)]( 
                    439: (this last one contains many examples of configuration files).
                    441: ## News with tin
                    443: The word *news* indicates the set of messages posted to the USENET newsgroups, a 
                    444: service available on the Internet. Each newsgroup contains articles related to a 
                    445: specific topic. Reading a newsgroup is different than reading a mailing list: 
                    446: when you subscribe to a mailing list you receive the articles by mail and you 
                    447: read them with a standard mail program like mutt, which you use also to send 
                    448: replies. News, instead, are read directly from a news server with a dedicated 
                    449: program called *newsreader* like, for example, tin. With tin you can subscribe 
                    450: to the newsgroups that you're interested in and follow the *threads*. A thread 
                    451: is a sequence of articles which all derive from an article that we could call 
                    452: *original*. In short, a message is sent to the group, someone answers, other 
                    453: people answer to those who answered in the first place and so on, creating a 
                    454: tree like structure of messages and replies: without a newsreader it is 
                    455: impossible to understand the correct sequence of messages.
                    457: After the installation of tin (from the package collection as usual) the only 
                    458: thing left to do is to write the name of the NNTP server in the file 
                    459: `/usr/pkg/etc/nntp/server`, which you may need to create first. For example:
                    463: Once this has been done, the program can be started with the command `tin`. On 
                    464: the screen something similar to the following example will be displayed:
                    466:     $ tin
                    467:     Connecting to
                    468: InterNetNews NNRP server INN 1.7.2 08-Dec-1997 ready (posting ok).
                    469:     Reading groups from active file...
                    470:     Checking for new groups...
                    471:     Reading attributes file...
                    472:     Reading newsgroups file...
                    473:     Creating newsrc file...
                    474:     Autosubscribing groups...
                    475:     Reading newsrc file...
                    477: Be patient when you connect for the first time, because tin downloads an immense 
                    478: list of newsgroups to which you can subscribe and this takes several minutes. 
                    479: When the download is finished, the program's main screen is displayed; usually 
                    480: no groups are displayed; to see the list of groups press `y`. To subscribe to a
                    481: group, move on the group's name and press `y`.
                    483: Once that you have subscribed to some newsgroups you can start tin more quickly 
                    484: with the command `tin -Q`. The search for new groups is disabled (`-q`), only 
                    485: active groups are searched (`-n`) and newsgroup description are not loaded 
                    486: (`-d`): it will not be possible to use the `y` (yank) command in tin. When tin 
                    487: is started with this option it can't tell if a newsgroup is moderated or not.
                    489: Note that if you are connecting from an internal network (like in our example), 
                    490: when you send ("post") a message the address at the beginning of the message 
                    491: will be wrong (because it is the internal address). To solve the problem, use 
                    492: the option `mail_address` in the tin configuration file (`~/.tin/tinrc`) or set 
                    493: the `REPLYTO` environment variable.

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