IMAP y POP3 con Dovecot - IMAP y POP3 con Dovecot

 El servicio de correo POP3 es muy práctico, permite leer los correos más rápido y te deja salvar en templates para enviarlos más tarde y con mayor formato. Pero todo tiene peros. No importa si usas Outlook Express o Mozilla Thunderbird, a todos nos ha pasado: estás un sábado en tu casa y recuerdas que el número de celular de tu hermana (que te urge) está en el cliente de correo de tu oficina. ¿No es desesperante no poder acceder a un correo porque lo bajaste en el cliente POP3 de otro lugar? ¿O que tal cuando tienes que rebootear pues bajaste el correo en Evolution y ahora necesitas verlo en Windows?

La solución es el servicio IMAP (Internet Message Access Protocol). Con una cuenta IMAP los correos se quedan en el servidor pero podemos gestionarlos y editarlos con nuestro cliente de correo como si fuese un POP3. Si en la oficina tiene correos leídos y templates con edición, puedes conectarte desde otro lugar (donde nunca hayas estado) y verá los mismos directorios y correos que dejaste en el otro lugar (o en el otro sistema operativo ;-) ). En este tutorial el MTA (Exim, Qmail, Postfix, etc.) ya debe estar funcionando y debemos tener la certeza de que funciona correctamente. Bien lo primero es lo primero:

# apt-get install dovecot-imapd dovecot-pop3d

Editamos el archivo /etc/dovecot/dovecot.conf para que se vea así:

|| Dovecot 1.0 configuration file # Default values are shown after each value, it's not required to uncomment # any of the lines. Exception to this are paths, they're just examples # with real defaults being based on configure options. The paths listed here # are for configure --prefix=/usr --sysconfdir=/etc --localstatedir=/var # --with-ssldir=/usr/share/ssl # Base directory where to store runtime data. #base_dir = /var/run/dovecot/ # Protocols we want to be serving: # imap imaps pop3 pop3s #protocols = imap imaps #

---

configurado para la MonoNeurona.org protocols = imap imaps pop3 pop3s # IP or host address where to listen in for connections. It's not currently # possible to specify multiple addresses. "*" listens in all IPv4 interfaces. # "[::]" listens in all IPv6 interfaces, but may also listen in all IPv4 # interfaces depending on the operating system. You can specify ports with # "host:port". #imap_listen = * #pop3_listen = * # IP or host address where to listen in for SSL connections. Defaults # to above non-SSL equilevants if not specified. #imaps_listen = #pop3s_listen = # Disable SSL/TLS support. #ssl_disable = no # PEM encoded X.509 SSL/TLS certificate and private key. They're opened before # dropping root privileges, so keep the key file unreadable by anyone but # root. Included doc/mkcert.sh can be used to easily generate self-signed # certificate, just make sure to update the domains in dovecot-openssl.cnf #ssl_cert_file = /usr/share/ssl/certs/dovecot.pem #ssl_key_file = /usr/share/ssl/private/dovecot.pem # SSL parameter file. Master process generates this file for login processes. # It contains Diffie Hellman and RSA parameters. #ssl_parameters_file = /var/run/dovecot/ssl-parameters.dat # How often to regenerate the SSL parameters file. Generation is quite CPU # intensive operation. The value is in hours, 0 disables regeneration # entirely. #ssl_parameters_regenerate = 24 # Disable LOGIN command and all other plaintext authentications unless # SSL/TLS is used (LOGINDISABLED capability) #disable_plaintext_auth = no # Use this logfile instead of syslog(). /dev/stderr can be used if you want to # use stderr for logging (ONLY /dev/stderr - otherwise it is closed). #log_path = # For informational messages, use this logfile instead of the default #info_log_path = # Prefix for each line written to log file. % codes are in strftime(3) # format. Note the extra space at the end of line. #log_timestamp = %b %d %H:%M:%S Login processes # Directory where authentication process places authentication UNIX sockets # which login needs to be able to connect to. The sockets are created when # running as root, so you don't have to worry about permissions. login_dir = /var/run/dovecot-login # chroot login process to the login_dir. Only reason not to do this is if you # wish to run the whole Dovecot without roots. #login_chroot = yes IMAP login process login = imap # Executable location. #login_executable = /usr/libexec/dovecot/imap-login # User to use for the login process. Create a completely new user for this, # and don't use it anywhere else. The user must also belong to a group where # only it has access, it's used to control access for authentication process. #login_user = dovecot # Set max. process size in megabytes. If you don't use # login_process_per_connection you might need to grow this. #login_process_size = 16 # Should each login be processed in it's own process (yes), or should one # login process be allowed to process multiple connections (no)? Yes is more # secure, espcially with SSL/TLS enabled. No is faster since there's no need # to create processes all the time. #login_process_per_connection = yes # Number of login processes to create. If login_process_per_user is # yes, this is the number of extra processes waiting for users to log in. #login_processes_count = 3 # Maximum number of extra login processes to create. The extra process count # usually stays at login_processes_count, but when multiple users start logging # in at the same time more extra processes are created. To prevent fork-bombing # we check only once in a second if new processes should be created - if all # of them are used at the time, we double their amount until limit set by this # setting is reached. This setting is used only if login_process_per_use is yes. #login_max_processes_count = 128 # Maximum number of connections allowed in login state. When this limit is # reached, the oldest connections are dropped. If login_process_per_user # is no, this is a per-process value, so the absolute maximum number of users # logging in actually login_processes_count * max_logging_users. #login_max_logging_users = 256 POP3 login process # Settings default to same as above, so you don't have to set anything # unless you want to override them. login = pop3 # Exception to above rule being the executable location. #login_executable = /usr/libexec/dovecot/pop3-login Mail processes # Maximum number of running mail processes. When this limit is reached, # new users aren't allowed to log in. #max_mail_processes = 1024 # Show more verbose process titles (in ps). Currently shows user name and # IP address. Useful for seeing who are actually using the IMAP processes # (eg. shared mailboxes or if same uid is used for multiple accounts). #verbose_proctitle = no # Show protocol level SSL errors. #verbose_ssl = no # Valid UID range for users, defaults to 500 and above. This is mostly # to make sure that users can't log in as daemons or other system users. # Note that denying root logins is hardcoded to dovecot binary and can't # be done even if first_valid_uid is set to 0. #first_valid_uid = 500 #last_valid_uid = 0 # Valid GID range for users, defaults to non-root/wheel. Users having # non-valid GID as primary group ID aren't allowed to log in. If user # belongs to supplementary groups with non-valid GIDs, those groups are # not set. #first_valid_gid = 1 #last_valid_gid = 0 ESTO LO PUSE YO mail_extra_groups = mail # ':' separated list of directories under which chrooting is allowed for mail # processes (ie. /var/mail will allow chrooting to /var/mail/foo/bar too). # This setting doesn't affect login_chroot or auth_chroot variables. # WARNING: Never add directories here which local users can modify, that # may lead to root exploit. Usually this should be done only if you don't # allow shell access for users. See doc/configuration.txt for more information. #valid_chroot_dirs = # Default MAIL environment to use when it's not set. By leaving this empty # dovecot tries to do some automatic detection as described in # doc/mail-storages.txt. There's a few special variables you can use: # # %u - username # %n - user part in user@domain, same as %u if there's no domain # %d - domain part in user@domain, empty if user there's no domain # %h - home directory # # You can also limit a width of string by giving the number of max. characters # after the '%' character. For example %1u gives the first character of # username. Some examples: # # maildir:/var/mail/%1u/%u/Maildir # mbox:~/mail/:INBOX=/var/mail/%u # mbox:/var/mail/%d/%n/:INDEX=/var/indexes/%d/%n # #default_mail_env = default_mail_env = mbox:~/mail:INBOX=/var/mail/%u # Space-separated list of fields to cache for all mails. Currently these # fields are allowed followed by a list of commands they speed up: # # Envelope - FETCH ENVELOPE and SEARCH FROM, TO, CC, BCC, SUBJECT, # SENTBEFORE, SENTON, SENTSINCE, HEADER MESSAGE-ID, # HEADER IN-REPLY-TO # Body - FETCH BODY # Bodystructure - FETCH BODY, BODYSTRUCTURE # MessagePart - FETCH BODY[1.2.3] (ie. body parts), RFC822.SIZE, # SEARCH SMALLER, LARGER, also speeds up BODY/BODYSTRUCTURE # generation. This is always set with mbox mailboxes, and # also default with Maildir. # # Different IMAP clients work in different ways, that's why Dovecot by default # only caches MessagePart which speeds up most operations. Whenever client # does something where caching could be used, the field is automatically marked # to be cached later. For example after FETCH BODY the BODY will be cached # for all new messages. Normally you should leave this alone, unless you know # what most of your IMAP clients are. Caching more fields than needed makes # the index files larger and generate useless I/O. # # With maildir there's one extra optimization - if nothing is cached, indexing # the maildir becomes much faster since it's not opening any of the mail files. # This could be useful if your IMAP clients access only new mails. #mail_cache_fields = MessagePart # Space-separated list of fields that Dovecot should never set to be cached. # Useful if you want to save disk space at the cost of more I/O when the fields # needed. #mail_never_cache_fields = # Workarounds for various client bugs: # oe6-fetch-no-newmail: # Never send EXISTS/RECENT when replying to FETCH command. Outlook Express # seems to think they are FETCH replies and gives user "Message no longer # in server" error. Note that OE6 still breaks even with this workaround # if synchronization is set to "Headers Only". # outlook-idle: # Outlook and Outlook Express never abort IDLE command, so if no mail # arrives in half a hour, Dovecot closes the connection. This is still # fine, except Outlook doesn't connect back so you don't see if new mail # arrives. #client_workarounds = # Dovecot can notify client of new mail in selected mailbox soon after it's # received. This setting specifies the minimum interval in seconds between # new mail notifications to client - internally they may be checked more or # less often. Setting this to 0 disables the checking. # NOTE: Evolution client breaks with this option when it's trying to APPEND. #mailbox_check_interval = 0 # Like mailbox_check_interval, but used for IDLE command. #mailbox_idle_check_interval = 30 # Allow full filesystem access to clients. There's no access checks other than # what the operating system does for the active UID/GID. It works with both # maildir and mboxes, allowing you to prefix mailboxes names with eg. /path/ # or ~user/. #mail_full_filesystem_access = no # Maximum allowed length for custom flag name. It's only forced when trying # to create new flags. #mail_max_flag_length = 50 # Save mails with CR+LF instead of plain LF. This makes sending those mails # take less CPU, especially with sendfile() syscall with Linux and FreeBSD. # But it also creates a bit more disk I/O which may just make it slower. #mail_save_crlf = no # Use mmap() instead of read() to read mail files. read() seems to be a bit # faster with my Linux/x86 and it's better with NFS, so that's the default. #mail_read_mmaped = no # Copy mail to another folders using hard links. This is much faster than # actually copying the file. This is problematic only if something modifies # the mail in one folder but doesn't want it modified in the others. I don't # know any MUA which would modify mail files directly. IMAP protocol also # requires that the mails don't change, so it would be problematic in any case. # If you care about performance, enable it. #maildir_copy_with_hardlinks = no # Check if mails' content has been changed by external programs. This slows # down things as extra stat() needs to be called for each file. If changes are # noticed, the message is treated as a new message, since IMAP protocol # specifies that existing message are immutable. #maildir_check_content_changes = no # Which locking methods to use for locking mbox. There's three available: # dotlock: Create <mailbox>.lock file. This is the oldest and most NFS-safe # solution. If you want to use /var/mail/ like directory, the users # will need write access to that directory. # fcntl : Use this if possible. Works with NFS too if lockd is used. # flock : May not exist in all systems. Doesn't work with NFS. # # You can use both fcntl and flock too; if you do the order they're declared # with is important to avoid deadlocks if other MTAs/MUAs are using both fcntl # and flock. Some operating systems don't allow using both of them # simultaneously, eg. BSDs. If dotlock is used, it's always created first. mbox_locks = fcntl # Should we create dotlock file even when we want only a read-lock? Setting # this to yes hurts the performance when the mailbox is accessed simultaneously # by multiple processes, but it's needed for reliable reading if no other # locking methods are available. #mbox_read_dotlock = no # Maximum time in seconds to wait for lock (all of them) before aborting. #mbox_lock_timeout = 300 # If dotlock exists but the mailbox isn't modified in any way, override the # lock file after this many seconds. #mbox_dotlock_change_timeout = 30 # umask to use for mail files and directories #umask = 0077 # Drop all privileges before exec()ing the mail process. This is mostly # meant for debugging, otherwise you don't get core dumps. Note that setting # this to yes means that log file is opened as the logged in user, which # might not work. It could also be a small security risk if you use single UID # for multiple users, as the users could ptrace() each others processes then. #mail_drop_priv_before_exec = no IMAP process # Executable location #imap_executable = /usr/libexec/dovecot/imap # Set max. process size in megabytes. Most of the memory goes to mmap()ing # files, so it shouldn't harm much even if this limit is set pretty high. #imap_process_size = 256 # Support for dynamically loadable modules. #imap_use_modules = no #imap_modules = /usr/lib/dovecot/imap POP3 process # Executable location #pop3_executable = /usr/libexec/dovecot/pop3 # Set max. process size in megabytes. Most of the memory goes to mmap()ing # files, so it shouldn't harm much even if this limit is set pretty high. #pop3_process_size = 256 # Support for dynamically loadable modules. #pop3_use_modules = no #pop3_modules = /usr/lib/dovecot/pop3 Authentication processes # You can have multiple processes; each time "auth = xx" is seen, a new # process definition is started. The point of multiple processes is to be # able to set stricter permissions to others. For example, plain/PAM # authentication requires roots, but if you also use digest-md5 authentication # for some users, you can authenticate them without any privileges in a # separate auth process. Just remember that only one auth process is asked # for the password, so you can't have different passwords with different # processes (unless they have different auth methods, and you're ok with # having different password for each method). # Authentication process name. auth = default # Space separated list of wanted authentication mechanisms: # plain digest-md5 anonymous auth_mechanisms = plain # Space separated list of realms for SASL authentication mechanisms that need # them. You can leave it empty if you don't want to support multiple realms. # Many clients simply use the first one listed here, so keep the default realm # first. #auth_realms = # Default realm to use if none was specified. #auth_default_realm = # Where user database is kept: # passwd: /etc/passwd or similiar, using getpwnam() # passwd-file <path>: passwd-like file with specified location # static uid=<uid> gid=<gid> home=<dir template>: static settings # vpopmail: vpopmail library # ldap <config path>: LDAP, see doc/dovecot-ldap.conf # pgsql <config path>: a PostgreSQL database, see doc/dovecot-pgsql.conf auth_userdb = passwd # Where password database is kept: # passwd: /etc/passwd or similiar, using getpwnam() # shadow: /etc/shadow or similiar, using getspnam() # pam [<service> | *]: PAM authentication # passwd-file <path>: passwd-like file with specified location # vpopmail: vpopmail authentication # ldap <config path>: LDAP, see doc/dovecot-ldap.conf # pgsql <config path>: a PostgreSQL database, see doc/dovecot-pgsql.conf auth_passdb = pam # Executable location #auth_executable = /usr/libexec/dovecot/dovecot-auth # Set max. process size in megabytes. #auth_process_size = 256 # User to use for the process. This user needs access to only user and # password databases, nothing else. Only shadow and pam authentication # requires roots, so use something else if possible. auth_user = root # Directory where to chroot the process. Most authentication backends don't # work if this is set, and there's no point chrooting if auth_user is root. #auth_chroot = # Number of authentication processes to create #auth_count = 1 # List of allowed characters in username. If the user-given username contains # a character not listed in here, the login automatically fails. This is just # an extra check to make sure user can't exploit any potential quote escaping # vulnerabilities with SQL/LDAP databases. If you want to allow all characters, # set this value to empty. #auth_username_chars = abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ01234567890.-_@ # Username to use for users logging in with ANONYMOUS SASL mechanism #auth_anonymous_username = anonymous # More verbose logging. Useful for figuring out why authentication isn't # working. #auth_verbose = no # digest-md5 authentication process. It requires special MD5 passwords which # /etc/shadow and PAM doesn't support, so we never need roots to handle it. # Note that the passwd-file is opened before chrooting and dropping root # privileges, so it may be 0600-root owned file. #auth = digest_md5 #auth_methods = digest-md5 #auth_realms = #auth_userdb = passwd-file /etc/passwd.imap #auth_passdb = passwd-file /etc/passwd.imap #auth_user = imapauth #auth_chroot = # if you plan to use only passwd-file, you don't need the two auth processes, # simply set "auth_methods = plain digest-md5" ||
El archivo dovecot.conf lo puedes ver aquí∞. Ahora reiniciamos dovecot:

# /etc/init.d/dovecot restart

¡Y ya esta! Ahora sólo debemos probar con Mozilla-Thunderbird creando una cuenta IMAP.