Bookmark and Share

Virtual Mailhosting System with Postfix Guide
Content: 1. Introduction 2. Postfix Basics 3. Courier-imap 4. Cyrus-sasl 5. SSL Certs for Postfix and Apache 6. Adding SSL and SASL support to Postfix 7. The vmail user 8. MySQL 9. Apache and phpMyAdmin 10. Configuring MySQL Authentication and vhosts 11. Squirrelmail 12. Mailman 13. Content Filtering and Anti-Virus 14. Wrap Up 15. Troubleshooting

1. Introduction

For most Gentoo users, a simple mail client and fetchmail will do. However, if you're hosting a domain with your system, you'll need a full blown MTA (Mail Transfer Agent). And if you're hosting multiple domains, then you'll definitely need something more robust to handle all of the email for your users. This system was designed to be an elegant solution to that problem.

A virtual mail system needs to be able to handle email for numerous domains with multiple users over a variety of interfaces. This presents some issues that must be dealt with. For instance, what if you have two users on different domains that want the same user name? If you are providing imap access and smtp-auth, how do combine the various authentication daemons into a single system? How do you provide security for the numerous components that comprise the system? How do you manage it all?

This howto will show you how to set up with a mail system capable of handling mail for as many domains as your hardware can handle, supports virtual mail users that don't require shell accounts, has domain specific user names, can authenticate web, imap, smtp, and pop3 clients against a single database, utilizes ssl for transport layer security, has a web interface, can handle mailing lists for any domain on the machine, and is controlled by a nice, central and easy mysql database.

There are quite a variety of ways to go about setting up a virtual mailhosting system. With so may options, another may be the best choice for your specific needs. Consider investigating {} and {} to explore your options.

The following packages are used in this setup: apache, courier-imap, courier-authlib postfix, mod_php, phpmyadmin, squirrelmail, cyrus-sasl, mysql, php, and mailman.

Make sure to turn on the following USE variables in /etc/make.conf before compiling the packages: USE="mysql imap libwww maildir sasl ssl". Otherwise you will most likely have to recompile things to get the support you need for all the protocols. Further, it's a good idea to turn off any other mail and network variables, like ipv6.
Important: You need a domain name to run a public mail server, or at least an MX record for a domain. Ideally you would have control of at least two domains to take advantage of your new virtual domain functionality.
Important: Make sure /etc/conf.d/hostname is set to the right hostname for your mail server. You can apply any changes you make to this file by running /etc/init.d/hostname restart. Verify your hostname is set correctly with hostname. Also verify that there are no conflicting entries in /etc/hosts.
Note: It is recommended that you read this entire document and familiarize yourself with all the steps before attempting the install. If you run into problems with any of the steps, check the troubleshooting guide at the end of this document. Also, not all the referenced packages are necessary, this set up is very flexible. For instance, if you do not desire a web interface, feel free to skip the squirrelmail section.

2. Postfix Basics
Code Listing 2.1: Install postfix
# emerge postfix Warning: Verify that you have not installed any other MTA, such as ssmtp, exim, or netqmail, or you will surely have BIG problems.

After postfix is installed, it's time to configure it. Change the following options in /etc/postfix/ Remember to replace $variables with your own names.
Code Listing 2.2: /etc/postfix/
myhostname = $ mydomain = $ inet_interfaces = all mydestination = $myhostname, localhost.$mydomain $mydomain mynetworks =, home_mailbox = .maildir/ local_destination_concurrency_limit = 2 default_destination_concurrency_limit = 10 Next change the following in /etc/postfix/ This will turn on verbose output for debugging:
Code Listing 2.3: /etc/postfix/
# service type private unpriv chroot wakeup maxproc command + args # (yes) (yes) (yes) (never) (50) # ========================================================================== (Just add the "-v" after the smtpd in the following line) smtp inet n - n - - smtpd -v Next, edit /etc/mail/aliases to add your local aliases. There should at least be an alias for root like: root: your@email.address.
Code Listing 2.4: Starting postfix for the first time
# /usr/bin/newaliases (This will install the new aliases. You only need to do this when you update or install aliases.) # /etc/init.d/postfix start Now that postfix is running, fire up your favorite console mail client and send yourself an email. I use mutt for all my console mail. Verify that postfix is delivering mail to local users, once that's done, we're on to the next step.
Note: I strongly recommend that you verify this basic postfix setup is functioning before you progress to the next step of the howto.

3. Courier-imap
Code Listing 3.1: Install courier-imap and courier-authlib
# emerge courier-imap courier-authlib Code Listing 3.2: Courier-imap configuration
# cd /etc/courier-imap (If you want to use the ssl capabilities of courier-imap or pop3, you'll need to create certs for this purpose. This step is recommended. If you do not want to use ssl, skip this step.) # nano -w pop3d.cnf # nano -w imapd.cnf (Change the C, ST, L, CN, and email parameters to match your server.) # mkpop3dcert # mkimapdcert Code Listing 3.3: Start the courier services you need.
# /etc/init.d/courier-imapd start # /etc/init.d/courier-imapd-ssl start # /etc/init.d/courier-pop3d start # /etc/init.d/courier-pop3d-ssl start Start up your favorite mail client and verify that all connections you've started work for receiving and sending mail. Of course, you won't be able to log on to any of the services because authentication hasn't been configured yet, but it is wise to check if the connections themselves work or not.

Now that the basics work, we're going to do a whole bunch of stuff at once to get the rest of the system running. Again, please verify that what we've installed already works before progressing.

4. Cyrus-sasl

Next we're going to install cyrus-sasl. Sasl is going to play the role of actually passing your auth variables to courier-auth, which will in turn pass that information to mysql for authentication of smtp users. For this howto, we'll not even try to verify that sasl is working until mysql is set up and contains a test user. Which is fine since we'll be authenticating against mysql in the end anyway.
Code Listing 4.1: Configuring and installing the cyrus-sasl ebuild
# emerge cyrus-sasl Next, edit /etc/sasl2/smtpd.conf.
Code Listing 4.2: Starting sasl
# nano -w /etc/sasl2/smtpd.conf mech_list: PLAIN LOGIN pwcheck_method: saslauthd # nano -w /etc/conf.d/saslauthd SASLAUTHD_OPTS="${SASLAUTH_MECH} -a rimap -r" SASLAUTHD_OPTS="${SASLAUTHD_OPTS} -O localhost" # /etc/init.d/saslauthd start 5. SSL Certs for Postfix and Apache

Next we're going to make a set of ssl certificates for postfix and apache.
Code Listing 5.1: Making ssl certicates
# cd /etc/ssl/ # nano -w openssl.cnf Change the following default values for your domain: countryName_default stateOrProvinceName_default localityName_default 0.organizationName_default commonName_default emailAddress_default. (If the variables are not already present, just add them in a sensible place.) # cd misc # ./ -newreq-nodes # ./ -newca # ./ -sign # cp newcert.pem /etc/postfix # cp newkey.pem /etc/postfix # cp demoCA/cacert.pem /etc/postfix (Now we do the same thing for apache.) # openssl req -new > new.cert.csr # openssl rsa -in privkey.pem -out new.cert.key # openssl x509 -in new.cert.csr -out new.cert.cert -req -signkey new.cert.key -days 365 (Just leave the resulting certificates here for now. We'll install them after Apache is installed.) 6. Adding SSL and SASL support to Postfix

Now edit the postfix config's to make it aware of your new sasl and ssl capabilities. Add the following parameters to the end of the file where they will be easy to find.
Code Listing 6.1: /etc/postfix/
# nano -w /etc/postfix/ smtpd_sasl_auth_enable = yes smtpd_sasl2_auth_enable = yes smtpd_sasl_security_options = noanonymous broken_sasl_auth_clients = yes smtpd_sasl_local_domain = (The broken_sasl_auth_clients option and the login auth method are for outlook and outlook express only and are undocumented. Isn't having to hack software for stupid, broken, M$ BS great? smtpd_sasl_local_domain appends a domain name to clients using smtp-auth. Make sure it's blank or your user names will get mangled by postfix and be unable to auth.) smtpd_recipient_restrictions = permit_sasl_authenticated, permit_mynetworks, reject_unauth_destination (The next two options enable outgoing encryption.) smtp_use_tls = yes smtp_tls_note_starttls_offer = yes smtpd_use_tls = yes #smtpd_tls_auth_only = yes smtpd_tls_key_file = /etc/postfix/newkey.pem smtpd_tls_cert_file = /etc/postfix/newcert.pem smtpd_tls_CAfile = /etc/postfix/cacert.pem smtpd_tls_loglevel = 3 smtpd_tls_received_header = yes smtpd_tls_session_cache_timeout = 3600s tls_random_source = dev:/dev/urandom (smtpd_tls_auth_only is commented out to ease testing the system. You can turn this on later if you desire.) # postfix reload Now we're going to verify that the config's we added were picked up by postfix. For this we are going to use telnet (provided by for instance net-misc/netkit-telnetd) although you can also use nc (provided by net-analyzer/netcat):
Code Listing 6.2: Verifying sasl and tls support
# telnet localhost 25 Trying Connected to localhost. Escape character is '^]'. 220 ESMTP Postfix EHLO 250-PIPELINING 250-SIZE 10240000 250-VRFY 250-ETRN 250-STARTTLS 250-AUTH LOGIN PLAIN 250-AUTH=LOGIN PLAIN 250-XVERP 250 8BITMIME ^] telnet> quit Verify that the above AUTH and STARTTLS lines now appear in your postfix install. As I said before, as it stands now AUTH will not work. that's because sasl will try to auth against it's sasldb, instead of the shadow file for some unknown reason, which we have not set up. So we're going to just plow through and set up mysql to hold all of our auth and virtual domain information.

7. The vmail user

Before we set up our virtual mailhosting environment, we create a functional user under which the virtual mailboxes will be hosted. For clarity's sake we will call this vmail:
Code Listing 7.1: Adding the vmail user
# adduser -d /home/vmail -s /bin/false -m vmail So now you've set up the vmail account. You can create multiple accounts if you want (to keep some structure in your set of virtual mail accounts). The user id, group id and home dirs are referenced in the MySQL tables.

Next to the user account we also need to create the location where the mailboxes will reside:
Code Listing 7.2: Creating mailboxes
# mkdir -p /home/vmail/ # chown -R vmail:vmail /home/vmail/ # maildirmake /home/vmail/ 8. MySQL

Next we're going to install and configure MySQL. You'll need the {genericmailsql.sql} dumpfile for this step.
Code Listing 8.1: Installing and configuring MySQL
# emerge mysql # /usr/bin/mysql_install_db (After this command runs follow the onscreen directions for adding a root password with mysql, otherwise your db will be wide open.) # /etc/init.d/mysql start # mysqladmin -u root -p create mailsql # mysql -u root -p mailsql < genericmailsql.sql # mysql -u root -p mysql mysql> GRANT SELECT,INSERT,UPDATE,DELETE -> ON mailsql.* -> TO mailsql@localhost -> IDENTIFIED BY '$password'; Query OK, 0 rows affected (0.02 sec) mysql> FLUSH PRIVILEGES; Query OK, 0 rows affected (0.00 sec) mysql> quit (Verify that the new mailsql user can connect to the mysql server.) # mysql -u mailsql -p mailsql Your new database has default values and tables set up for two domains. The following tables are included:
* alias - local email alias and mailman alias information.
* relocated - relocated user email address maps
* transport - default mail transport information for all domains you are hosting
* users - all user account information
* virtual - virtual domain email alias maps
Code Listing 8.2: alias table sample
id alias destination 1 root 2 postmaster Code Listing 8.3: user table sample
(Line wrapped for clarity.) id email clear name uid gid homedir \ maildir quota postfix 10 $password realname virtid virtid /home/vmail \ /home/vmail/ y 13 $password realname localid localid /home/foo \ /home/foo/.maildir/ y The values of the virtid uid and gid should be those of the vmail user and group.
Code Listing 8.4: transport table sample
id domain destination 1 local: 2 virtual: Code Listing 8.5: virtual table sample
id email destination 3 other@email.address 9. Apache and phpMyAdmin

Next we'll set up apache and add an interface to interact with the database more easily.
Code Listing 9.1: Setting up apache and phpmyadmin
# emerge apache phpmyadmin There are plenty of guides out there about how to set up apache with php, including guides provided by the {Gentoo PHP Project}. There are also numerous posts on {} detailing how to solve problems with the installation. So, that said, we're not going to cover it here. Set up the apache and php installs, then continue with this howto. Now, a word for the wise: .htaccess the directory that you put phpmyadmin in. If you do not do this, search engine spiders will come along and index the page which in turn will mean that anyone will be able to find your phpmyadmin page via google and in turn be able to come change your database however they want which is BAD! There are many howtos on this including: {}.

Now we're going to install the Apache certificates we made previously. The Apache-SSL directives that you need to use the resulting cert are:
* SSLCertificateFile /path/to/certs/new.cert.cert
* SSLCertificateKeyFile /path/to/certs/new.cert.key
Code Listing 9.2: Install Apache SSL certificates
# cp /etc/ssl/misc/new.cert.cert /etc/apache2/ssl/ # cp /etc/ssl/misc/new.cert.key /etc/apache2/ssl/ # cd /etc/apache2/vhosts.d (Check if you have an ssl-vhost template already. Copy that one instead of the default_vhost if that is the case) # cp 00_default_vhost.conf ssl-vhost.conf # nano -w ssl-vhost.conf (Change the following parameters) NameVirtualHost ServerName ServerAdmin your@email.address DocumentRoot "/var/www/localhost/htdocs/phpmyadmin"; ... SSLCertificateFile /etc/apache2/ssl/new.cert.cert SSLCertificateKeyFile /etc/apache2/ssl/new.cert.key SSLEngine on ... # nano -w /etc/conf.d/apache2 (Add -D SSL -D PHP5 to the APACHE2_OPTS) # /etc/init.d/apache2 restart Next, configure phpMyAdmin.
Code Listing 9.3: Configuring phpMyAdmin
# cd /var/www/localhost/htdocs/phpmyadmin # cp # nano -w (Change the following parameters.) $cfg['blowfish_secret'] = 'someverysecretpassphraze'; $cfg['Servers'][$i]['host'] = 'localhost'; // MySQL hostname $cfg['Servers'][$i]['controluser'] = 'mailsql'; // MySQL control user settings // (this user must have read-only $cfg['Servers'][$i]['controlpass'] = '$password'; // access to the "mysql/user" // and "mysql/db" tables) $cfg['Servers'][$i]['user'] = 'mailsql'; // MySQL user $cfg['Servers'][$i]['password'] = '$password'; // MySQL password Now enter the phpmyadmin page and browse the tables. You'll want to add in your local aliases, edit your user table to add a test user, and change your transport table to add information about your domains. The default values supplied with the dumpfile should be a sufficient guide to what values need to go where. Make sure that if you put information in the database that it is accurate. For instance, make sure the local user's home dir exists and that the correct uid/gid values are in place. The maildirs should be created automatically by postfix when the user receives their first email. So, in general, it's a good idea to send a "Welcome" mail to a new user after you setup their account to make sure the .maildir gets created.

10. Configuring MySQL Authentication and vhosts

Next we'll reconfigure our authentication to use the mailsql database in courier-imap and postfix. In all of the following examples, replace $password with the password you set for the mailsql mysql user.
Code Listing 10.1: Configuring authentication
# nano -w /etc/courier/authlib/authdaemonrc authmodulelist="authmysql authpam" # nano -w /etc/courier/authlib/authmysqlrc MYSQL_SERVER localhost MYSQL_USERNAME mailsql MYSQL_PASSWORD $password MYSQL_DATABASE mailsql MYSQL_USER_TABLE users (Make sure the following line is commented out since we're storing plaintext.) #MYSQL_CRYPT_PWFIELD crypt MYSQL_CLEAR_PWFIELD clear MYSQL_UID_FIELD uid MYSQL_GID_FIELD gid MYSQL_LOGIN_FIELD email MYSQL_HOME_FIELD homedir MYSQL_NAME_FIELD name MYSQL_MAILDIR_FIELD maildir # /etc/init.d/courier-authlib restart # /etc/init.d/saslauthd restart We're almost there, I promise! Next, set up the rest of the necessary configs for postfix to interract with the database for all its other transport needs. Remember to replace each value with the name of your own user, user id, password, alias, email address, and so on.
Code Listing 10.2: /etc/postfix/
# nano -w /etc/postfix/ # user = mailsql password = $password dbname = mailsql table = alias select_field = destination where_field = alias hosts = unix:/var/run/mysqld/mysqld.sock Code Listing 10.3: /etc/postfix/
# nano -w /etc/postfix/ # user = mailsql password = $password dbname = mailsql table = relocated select_field = destination where_field = email hosts = unix:/var/run/mysqld/mysqld.sock Code Listing 10.4: /etc/postfix/ (optional)
# nano -w /etc/postfix/ # user = mailsql password = $password dbname = mailsql table = transport select_field = destination where_field = domain hosts = unix:/var/run/mysqld/mysqld.sock Code Listing 10.5: /etc/postfix/ (optional)
# nano -w /etc/postfix/ # user = mailsql password = $password dbname = mailsql table = users select_field = gid where_field = email additional_conditions = and postfix = 'y' hosts = unix:/var/run/mysqld/mysqld.sock Code Listing 10.6: /etc/postfix/
# nano -w /etc/postfix/ # user = mailsql password = $password dbname = mailsql table = users select_field = maildir where_field = email additional_conditions = and postfix = 'y' hosts = unix:/var/run/mysqld/mysqld.sock Code Listing 10.7: /etc/postfix/ (optional)
# nano -w /etc/postfix/ # user = mailsql password = $password dbname = mailsql table = users select_field = uid where_field = email additional_conditions = and postfix = 'y' hosts = unix:/var/run/mysqld/mysqld.sock Code Listing 10.8: /etc/postfix/
# nano -w /etc/postfix/ # user = mailsql password = $password dbname = mailsql table = virtual select_field = destination where_field = email hosts = unix:/var/run/mysqld/mysqld.sock Lastly, edit /etc/postfix/ one more time.
Code Listing 10.9: /etc/postfix/
# nano -w /etc/postfix/ (Ensure that there are no other alias_maps definitions) alias_maps = mysql:/etc/postfix/ relocated_maps = mysql:/etc/postfix/ local_transport = local local_recipient_maps = $alias_maps $virtual_mailbox_maps unix:passwd.byname virtual_transport = virtual (The domains listed by the mydestination should not be listed in the virtual_mailbox_domains parameter) virtual_mailbox_domains =, $ virtual_minimum_uid = 1000 (Substitute $vmail-gid with the GID of the vmail group) virtual_gid_maps = static:$vmail-gid virtual_mailbox_maps = mysql:/etc/postfix/ virtual_alias_maps = mysql:/etc/postfix/ (Substitute $vmail-uid with the UID of the vmail user) virtual_uid_maps = static:$vmail-uid virtual_mailbox_base = / #virtual_mailbox_limit = For security reasons you should change the permissions of the various /etc/mail/mysql-*.cf:
Code Listing 10.10: Changing file permission
# chmod 640 /etc/postfix/mysql-*.cf # chgrp postfix /etc/postfix/mysql-*.cf As of Postfix 2.0.x, there were a number of significant changes over the 1.1.x release. Notably the transport, virtual-gid, and virtual-uid tables are no longer necessary. The tables are still included if you wish to use them.
Note: It is recommended that you read VIRTUAL_README included with the postfix docs for more information.
Code Listing 10.11: Make postfix reload its tables
# postfix reload Now, if all went well, you should have a functioning mailhost. Users should be able to authenticate against the sql database, using their full email address, for pop3, imap, and smtp. I would highly suggest that you verify that everything is working at this point. If you run into problems (with as many things as this setup has going on, it's likely that you will) check the troubleshooting section of this howto.

11. Squirrelmail
Code Listing 11.1: Install squirrelmail
# emerge squirrelmail (Install squirrelmail to localhost so that it's accessed by http://localhost/mail) (Substitute 1.4.3a-r2 with the version you use) # webapp-config -I -h localhost -d /mail squirrelmail 1.4.3a-r2 # cd /var/www/localhost/htdocs/mail/config # perl ./ (Change your Organization, Server, and Folder settings for squirrelmail. Now you should be able to login to squirrelmail, again - with your full email address, and use your new webmail setup.) 12. Mailman

Last step: mailman. The new version of mailman has very nice virtual domain support, which is why I use it, not to mention it's really a great package. To get this package installed and working correctly for virtual domains is going to require a bit of hacking. I really recommend reading all of the mailman documentation, including README.POSTFIX.gz, to understand what's being done here.
Code Listing 12.1: Install mailman
# emerge mailman Code Listing 12.2: Setting defaults: Mailman/
# nano -w /usr/local/mailman/Mailman/ (Change the values below to reflect your primary domain, virtuals will be set next.) DEFAULT_EMAIL_HOST = '' DEFAULT_URL_HOST = '' Code Listing 12.3: mailman config:
# nano -w /usr/local/mailman/Mailman/ MTA = "Postfix" POSTFIX_STYLE_VIRTUAL_DOMAINS = ['', ''] add_virtualhost('', '') add_virtualhost('', '') (This is required for your virtual domains for mailman to function.) Code Listing 12.4: And last but not least
(Once that's finished, add your first list.) # su mailman # cd ~ # ./bin/newlist --urlhost='' --emailhost='' test Enter the email of the person running the list: your@email.address Initial test password: Hit enter to continue with test owner notification... (Virtual domain lists may also be specified with style list names.) # ./bin/genaliases (Now that your aliases have been generated, verify that they were added successfully.) # nano -w data/aliases # STANZA START: test # CREATED: test: "|/usr/local/mailman/mail/mailman post test" test-admin: "|/usr/local/mailman/mail/mailman admin test" test-bounces: "|/usr/local/mailman/mail/mailman bounces test" test-confirm: "|/usr/local/mailman/mail/mailman confirm test" test-join: "|/usr/local/mailman/mail/mailman join test" test-leave: "|/usr/local/mailman/mail/mailman leave test" test-owner: "|/usr/local/mailman/mail/mailman owner test" test-request: "|/usr/local/mailman/mail/mailman request test" test-subscribe: "|/usr/local/mailman/mail/mailman subscribe test" test-unsubscribe: "|/usr/local/mailman/mail/mailman unsubscribe test" # STANZA END: test (Create the required mailman list) # ./bin/newlist mailman # ./bin/genaliases (Return to the root user) # exit # /etc/init.d/mailman start # rc-update add mailman default (To start mailman at once and on every reboot.) Code Listing 12.5: Adding mailman alias support to postfix
# nano -w /etc/postfix/ owner_request_special = no recipient_delimiter = + (Read README.POSTFIX.gz for details on this.) alias_maps = hash:/usr/local/mailman/data/aliases, mysql:/etc/postfix/ virtual_alias_maps = hash:/usr/local/mailman/data/virtual-mailman, mysql:/etc/postfix/ (This adds mailman alias file support to postfix You may of course use the mysql tables for this, but I hate doing that by hand. Also, if you are not using virtual domains, adding the virtual alias maps to postfix may cause problems, be warned.) You should now be able to setup mailing lists for any domain on your box. Last note on this, make sure you run all mailman commands as the user mailman (su mailman) or else the permissions will be wrong and you'll have to fix them. Read the mailman doc's for more information on setting up and managing mailman lists.

13. Content Filtering and Anti-Virus

For content filtering and Anti-Virus, please consult our {mail filtering gateway guide}.

14. Wrap Up

Ok, you're all set, edit /etc/postfix/ and turn off verbose mode for production use. You'll probably also want to add the services to your startup routine to make sure everything comes back up on a reboot. Make sure to add all the services you're using - apache, mysql, saslauthd, postfix, courier-imapd, courier-imapd-ssl, courier-pop3d, and courier-pop3d-ssl are all up to your decision on what access you want to provide. I generally have all the services enabled.
Code Listing 14.1: Wrap up
# postfix reload # rc-update add $service default Have fun!

15. Troubleshooting


Troubleshooting: This is a short troubleshooting guide for the set up we've detailed how to install here. It is not exhaustive, but meant as a place to get you started in figuring out problems. With a complicated setup such as this, it's imperative that you narrow down the problem to the particular component that is malfunctioning. In general I do that by following a few steps. Start from the base of the system and work your way up, ruling out components that work along the way until you discover which component is having the problem.

Step 1: Check your config files

Typos are killers, especially when dealing with authentication systems. Scan your config's and mailsql database for typo's. You can debug all you want, but if you're not passing the right information back and forth to your mail system, it's not going to work. If you make a change to a config file for a service, make sure you restart that service so that the config change gets picked up.
Code Listing 15.1: How to restart a service
# /etc/init.d/service restart Step 2: Are all the necessary services actually running?

If it's not running, start it up. It's awful hard to debug a service that isn't running. Sometimes a service will act like it's started but still not function. Sometimes, when a bad config is used, or a bad transmission comes into a mail component, the service will hang and keep the port from being used by another process. Sometimes you can detect this with netstat. Or, if you've been at it awhile, just take a break and reboot your box in the meantime. That will clear out any hung services. Then you can come back fresh and try it again.
Code Listing 15.2: Checking the status of a service
# /etc/init.d/$service status # netstat -a | grep $service (or $port) Step 3: Are all the service using the current config's?

If you've recently made a change to a config file, restart that service to make sure it's using the current version. Some of the components will dump their current config's to you, like postfix.
Code Listing 15.3: Some services can dump their current config
# apache2ctl fullstatus (needs lynx installed) # apache2ctl configtest (checks config sanity) # postconf -n (will tell you exactly what param's postfix is using) # /etc/init.d/$service restart Step 4: Check the logs

Repeat after me, logs are my friend. My next troubleshooting stop is always the logs. Sometimes it's helpful to try a failed operation again then check the logs so that the error message is right at the bottom (or top depending on your logger) instead of buried in there somewhere. See if there is any information in your log that can help you diagnose the problem, or at the very least, figure out which component is having the problem.
Code Listing 15.4: Checking the logs
# kill -USR1 `ps -C metalog -o pid=`(to turn off metalog buffering) # nano -w /var/log/mail/current # cat /var/log/mysql/mysql.log # tail /var/log/apache2/error_log You may also find the debug_peer parameters in helpful. Setting these will increase log output over just verbose mode.
Code Listing 15.5: adding debug_peer support
# nano -w /etc/postfix/ debug_peer_level = 5 debug_peer_list = $ (Uncomment one of the suggested debugger commands as well.) Step 5: Talk to the service itself

SMTP, IMAP, and POP3 all respond to telnet sessions. As we've seen earlier when we verified postfix's config. Sometimes it's helpful to open a telnet session to the service itself and see what's happening.
Code Listing 15.6: Connect to a service with telnet
# telnet localhost $port (SMTP is 25, IMAP is 143, POP3 is 110. You should receive at least an OK string, letting you know that the service is running and ready to respond to requests.) Trying Connected to localhost. Escape character is '^]'. * OK Courier-IMAP ready. Copyright 1998-2002 Double Precision, Inc. Step 6: Sometimes only the big guns will give you the information you need: strace

You should have this installed anyway. This is an invaluable tool for debugging software. You can start commands from the command line with strace and watch all the system calls as they happen. It often dumps a huge amount of information, so you'll either need to watch it realtime as you retry a failed transaction with the mail system, or dump the output to a file for review.
Code Listing 15.7: Using strace
# emerge strace # strace $command # strace -p `ps -C $service -o pid=`