“UbuntuHelp:Dovecot”的版本间的差异

2009年5月12日 (二) 16:30的最新版本

文章出处:

https://help.ubuntu.com/community/Dovecot

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Introduction

Dovecot is a Mail Delivery Agent, written with security primarily in mind. It supports the major mailbox formats: mbox or Maildir. It is a simple and easy to install MDA. This guide explains how to set it up as an IMAP or POP3 server. For alternate IMAP/POP3 servers see Courier or Cyrus. To configure Dovecot to use LDAP for user authentication see DovecotLDAP

Installation

The installation is extremely simple, just install the following packages: dovecot-imapd dovecot-pop3d For example, using aptitude:

sudo aptitude install dovecot-imapd dovecot-pop3d

Configuration

To configure dovecot, you edit the file /etc/dovecot/dovecot.conf. There are a couple of choices which you need to make.

Choice of Protocols

The choice is broadly between two protocols: IMAP and POP3. POP3 is useful when e-mail is checked from only one computer, and is best for people who download their email, and then work offline. IMAP is the better choice when you would like to check your mail from multiple computers, at work and home, for example. IMAP has the added benefit of accessing folders on the server, allowing you to organize your e-mail, and access it from anywhere. For more information, see the wikipedia articles on POP3 and IMAP. IMAPS and POP3S are more secure than the simple IMAP and POP3 because they use TLS encryption to connect. Once you have chosen, amend the following line in the file /etc/dovecot/dovecot.conf:

protocols = pop3 pop3s imap imaps

This enables those protocols when dovecot is started. Note: if you like, you can enable all the above protocols, but if you prefer, simply enable one or more of them. In addition, add the following line in pop3 section in the /etc/dovecot/dovecot.conf:

pop3_uidl_format = %08Xu%08Xv

Choice of Mailboxes

Dovecot currently supports maildir and mbox formats. They are the most commonly used mailbox formats. They both have their own benefits, discussed here. If you have trouble figuring out what you are using, it's most likely mbox. Maildir mails are almost always stored in ~/Maildir/ directory, which contains cur/, new/ and tmp/ subdirectories. In maildir each mail is stored in a separate file, while with the mbox format one file contains all mails in the mailbox. Files in /var/mail/ are nearly always mbox files, one for each user. If you have trouble figuring out what you should be using, choose maildir. It's overall more scalable and it can't get corrupted. To configure dovecot to use your chosen mailbox, you need to edit the file /etc/dovecot/dovecot.conf. If you're using Ubuntu 6.06 (Dapper) or Ubuntu 6.10 (Edgy) amend the following line:

default_mail_env = maildir:~/Maildir (for maildir)

or

default_mail_env = mbox:~/mail:INBOX=/var/mail/%u (for mbox)

As of Ubuntu 7.04 (Feisty) the default_mail_env setting changed to mail_location, so to configure Dovecot for your mailbox format use:

mail_location = maildir:~/Maildir (for maildir)
or
mail_location = mbox:~/mail:INBOX=/var/mail/%u (for mbox)

Note: You will also need to configure your MTA to transfer the incoming mail to this type of mailbox. (If you installed Postfix with instructions from the previous|wiki, then choose mbox.)

Setting up Maildir

Do these steps ONLY if you want Maildir. This setup will put the Maildir in each user's home directory. If you are using Postfix as your MTA, then add the following line to your /etc/postfix/main.cf file:

home_mailbox = Maildir/

Edit /etc/dovecot/dovecot.conf:

default_mail_env = maildir:/home/%u/Maildir

or if you're using Ubuntu 7.04 (Feisty) or newer:

mail_location = maildir:/home/%u/Maildir

It's a good idea to pre-create the Maildir for future users:

sudo maildirmake.dovecot /etc/skel/Maildir
sudo maildirmake.dovecot /etc/skel/Maildir/.Drafts
sudo maildirmake.dovecot /etc/skel/Maildir/.Sent
sudo maildirmake.dovecot /etc/skel/Maildir/.Trash
sudo maildirmake.dovecot /etc/skel/Maildir/.Templates

Then, for an existent user:

sudo cp -r /etc/skel/Maildir /home/myuser/
sudo chown -R myuser:usergroup /home/myuser/Maildir
sudo chmod -R 700 /home/myuser/Maildir

Test

Start dovecot:

/etc/init.d/dovecot start

To check that it is running, type the command ps -A|grep dovecot. You should see the dovecot service running. If you have enabled imap, or pop3, you can also try to log in with the commands telnet localhost pop3 or telnet localhost imap2. If you see something like the following, the installation has been successful.

matt@kalliope:~$ telnet localhost pop3
Trying localhost...
Connected to localhost.
Escape character is '^]'.
+OK dovecot ready.

Authentication

If you've gotten this far, dovecot is working but may still have to be configured so that users can login to check their mail. The simplest login method is sending the user login info in plain text and allowing access only to users that already have UNIX access (ie. in /etc/passwd) to the machine dovecot is running on. Allowing access only to users that already have UNIX access is the dovecot default, nothing has to be done to configure this. And, plain text logins are enabled by default when using secure protocols. To enable plain text logins when not using a secure protocol, put the following line in /etc/dovecot/dovecot.conf:

disable_plaintext_auth = no

If you are using the secure protocols imaps or pop3s, plain text logins is not a problem, because the transfer is done via an encrypted connection. If you are using simply imap or pop3, and will be connecting to the server from outside your local computer or home network, it is a good idea to configure more secure authentication. For further details about how to do this, see this page on the dovecot website.

SSL

To configure dovecot to use SSL, edit the file /etc/dovecot/dovecot.conf and amend the following lines (in some cases you may simply have to remove the # symbol from the beginning of the line):

ssl_cert_file = /etc/ssl/certs/ssl-cert-snakeoil.pem
ssl_key_file = /etc/ssl/private/ssl-cert-snakeoil.key
ssl_disable = no

The cert and key files are created automatically by dovecot when you install it. Please note, that these keys are not signed and will give "bad signature" errors when connecting from a client. To avoid this, you can use commercial certificates, or even better, you can use your own SSL certificates. Hopefully, a guide will appear soon on this wiki on how to do this. In the meantime, here are some good ones: this guide on the Linux howto database, and this guide on the Debian Administration website.

Accessing from Outside

In order to access your mail server from another computer, you'll have to configure your firewall or router to allow connections to the server on the necessary ports:

• IMAP - 143
• IMAPS - 993
• POP3 - 110
• POP3S - 995

You'll also need to uncomment following line in /etc/dovecot/dovecot.conf:

listen = *

Email Clients

Thunderbird

To use with Thunderbird, edit the file /etc/dovecot/dovecot.conf:

protocol imap {
 ...
login_greeting_capability = yes
imap_client_workarounds = tb-extra-mailbox-sep
}

In Thunderbird, under Server Settings -> Advanced, uncheck "Show only subscribed folders". Note: this guide has been tested on Ubuntu 6.06 (Dapper), Ubuntu 7.06 (Feisty), and Ubuntu 7.10 (Gutsy).

Related Articles

• POP3Aggregator - this guide explains how to set up an IMAP mail server with Dovecot that will download your mail from an external POP3 server, and allow you to access the mail using any IMAP-compatible email client.

See also

• The Dovecot Wiki