UbuntuHelp:GmailPostfixFetchmail
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目录
Introduction
This page is for those who wish to use Postfix and Fetchmail to access a single Gmail account. The setup presented here is limited: it is intended for a machine with a single user who wishes to read and send e-mail using an old-fashioned client such as mutt or Emacs GNUS. The setup presented is intended to be as simple and as close to a standard Ubuntu configuration as possible. The Postfix setup does not verify the Gmail SMTP server certificate; the reason for this is discussed in the appendix. If you use Evolution or a similar modern e-mail client, you do not need to use this setup: your client can connect directly to the Gmail POP3 and SMTP services. For help with Evolution, see UsingGmailWithEvolution. For help with Thunderbird, see Google's help at http://mail.google.com/support/bin/answer.py?answer=38343
Assumed reader knowledge
You should be familiar with package installation, and be able to edit text configuration files. You should also be familiar with terms like POP3, SMTP and SSL.
References
- http://prantran.blogspot.com/2007/01/getting-postfix-to-work-on-ubuntu-with.html
- http://souptonuts.sourceforge.net/postfix_tutorial.html
- http://www.postfix.com/TLS_README.html
- http://www.postfix.com/SASL_README.html
- http://www.postfix.com/ADDRESS_REWRITING_README.html
Packages needed
You will need the postfix and fetchmail packages. See InstallingSoftware for more on installing packages.
Setting up your Gmail account
You will need to enable POP access for your Gmail account. See UsingGmailWithEvolution for more.
Example username
In all the examples below, I've assumed that the username on the
Ubuntu system is jane, and that the Gmail username is
[email protected], with password doeadeer. You obviously need to
replace these with your local username, your Gmail username and Gmail
password as appropriate.
Configuring Postfix
To setup Postfix, you will need to create 5 files:
- /etc/postfix/main.cf
- /etc/postfix/generic
- /etc/postfix/generic.db
- /etc/postfix/passwd
- /etc/postfix/passwd.db
You will need root access to create and edit these files; see RootSudo for more on gaining root access.
Stop Postfix
It's not necessary to do so, but if you wish to stop Postfix while configuring, run (as root)
/etc/init.d/postfix stop
/etc/postfix/main.cf
When you install Postfix you will be prompted to make configuration choices. You can choose "No configuration"; in this case no configuration file will be created, and you can use the contents below. The configuration choices used to create it are listed in the Appendix. This is the Postfix configuration file /etc/postfix/main.cf:
# See /usr/share/postfix/main.cf.dist for a commented, more complete version
# Debian specific: Specifying a file name will cause the first
# line of that file to be used as the name. The Debian default
# is /etc/mailname.
#myorigin = /etc/mailname
smtpd_banner = $myhostname ESMTP $mail_name (Ubuntu)
biff = no
# appending .domain is the MUA's job.
append_dot_mydomain = no
# Uncomment the next line to generate "delayed mail" warnings
#delay_warning_time = 4h
# TLS parameters
smtpd_tls_cert_file=/etc/ssl/certs/ssl-cert-snakeoil.pem
smtpd_tls_key_file=/etc/ssl/private/ssl-cert-snakeoil.key
smtpd_use_tls=yes
smtpd_tls_session_cache_database = btree:${queue_directory}/smtpd_scache
smtp_tls_session_cache_database = btree:${queue_directory}/smtp_scache
# See /usr/share/doc/postfix/TLS_README.gz in the postfix-doc package for
# information on enabling SSL in the smtp client.
myhostname = localhost
alias_maps = hash:/etc/aliases
alias_database = hash:/etc/aliases
mydestination = localhost, localhost.localdomain
relayhost =
mynetworks = 127.0.0.0/8
mailbox_size_limit = 0
recipient_delimiter = +
inet_interfaces = loopback-only
inet_protocols = all
smtp_tls_loglevel=1
smtp_tls_security_level=encrypt
smtp_sasl_auth_enable=yes
smtp_sasl_password_maps=hash:/etc/postfix/sasl/passwd
smtp_sasl_security_options = noanonymous
smtp_generic_maps=hash:/etc/postfix/generic
relayhost=[smtp.gmail.com]:587
An explanation of each non-standard line (following the comment "non debconf entries start here") is given in the Appendix.
/etc/postfix/generic and /etc/postfix/generic.db
The generic file tells Postfix how to map local e-mail addresses to
Internet addresses when mail is sent via SMTP. Postfix rewrites
"From:" headers to make e-mail appear to come from
[email protected] instead of jane@localhost.
The /etc/postfix/generic is a plain text file, and should look as
follows:
jane@localhost [email protected]
/etc/postfix/generic.db is generated from this using the postmap command:
cd /etc/postfix postmap generic
/etc/postfix/sasl/passwd and /etc/postfix/sasl/passwd.db
The passwd file contains your Gmail password. Like /etc/postfix/generic file discussed above, it is a plain text file; it should look as follows:
[smtp.gmail.com]:587 [email protected]:doeadeer
To create passwd.db, and set ownership and permissions appropriately, run the following commands:
cd /etc/postfix/sasl postmap passwd chown root.root passwd passwd.db chmod 600 passwd passwd.db
Start or reload Postfix
If you previously stopped Postfix, restart it with
/etc/init.d/postfix start
If you didn't stop Postfix, force it to reload its configuration with
postfix reload
Testing
Postfix provides a means of testing its address rewriting rules using the sendmail command with the '-bv' option. If the mail would be sent externally (i.e., via smtp.gmail.com), the command will cause sendmail to connect and authenticate to smtp.gmail.com, which makes it a convenient way to test the Postfix setup. One possibly inconvenient feature of sendmail -bv is that the result is mailed to the user who ran the command; thus, if mail is utterly misconfigured, you will never receive the result. If you suspect this is the case, you can check /var/log/mail.log to see what went wrong. To check that basic delivery works, run the following command as a normal user (replacing "jane", as elsewhere, with your username):
sendmail -bv jane
You should receive a mail starting with:
This is the mail system at host localhost. Enclosed is the mail delivery report that you requested. The mail system <jane@localhost> (expanded from <jane>): delivery via local: delivers to mailbox
If this didn't work, make sure that Postfix is running. To check that Postfix can successfully connect to gmail, run
sendmail -bv [email protected]
You should receive a mail starting with:
This is the mail system at host localhost. Enclosed is the mail delivery report that you requested. The mail system <[email protected]>: delivery via smtp.gmail.com[66.249.91.109]:587: 250 2.1.5 OK
Potential problems with this are discussed in the following section.
Potential Postfix problems
Cannot find password
If you get an error message like this:
<[email protected]>: delivery via smtp.gmail.com[66.249.91.109]:587: host smtp.gmail.com[66.249.91.109] said: 530 5.5.1 Authentication Required c24sm1773006ika (in reply to MAIL FROM command)
then Postfix cannot figure out what password to send gmail; make sure that the smtp_sasl_password_maps entry in /etc/postfix/main.cf is correct, that /etc/postfix/sasl/passwd is correct, and that you've created /etc/postfix/sasl/passwd.db.
No mechanism available
If you get an error message like this:
SASL authentication failed; cannot authenticate to server smtp.gmail.com[66.249.91.109]: no mechanism available
you have probably forgotten the smtp_sasl_security_options line in /etc/postfix/main.cf.
Configuring Fetchmail
The setup presented here configures the system-wide fetchmail service, which is by default always running; for this use /etc/fetchmailrc is the configuration file. If you want to run fetchmail as your normal user you should use ~/.fetchmailrc; that case is not further discussed here. Unlike the Postfix setup above, the fetchmail configuration presented here will verify the Gmail POP3 server's certificate.
Stop the fetchmail service
To stop fetchmail while configuring it, run
/etc/init.d/fetchmail stop
/etc/fetchmail.rc
The file /etc/fetchmailrc should look as follows:
set syslog set daemon 240 poll pop.gmail.com with nodns, with protocol POP3 user "[email protected]" there is jane here, with password doeadeer, with ssl, sslcertck;
A detailed explanation is given in the appendix, though fetchmail's configuration language hopefully makes it clear. Since this file contains your Gmail password, you may wish to give it restrictive read permission:
chmod 600 /etc/fetchmailrc
Testing
To test your configuration, run fetchmail as below; this should be run as root, since it reads /etc/fetchmailrc.
fetchmail -v -d0 -f /etc/fetchmailrc
Take a look at /var/log/mail.log (e.g., using less /var/log/mail.log)
to see that the connection was successful.
Restart fetchmail
Once your configuration is working, you can restart fetchmail with
/etc/init.d/fetchmail start
Appendix
Debconf choices for main.cf above
For the record, the main.cf above was created with dpkg-reconfigure postfix with the following selections:
General type of configuration: Satellite system Mail for root: <blank> (default) Mail name: localhost (default) SMTP relay host: <blank> (default is smtp.localdomain) Other destinations to accept mail for: localhost, localhost.localdomain, localhost (default) Synchronous updates: no (default) Local networks: 127.0.0.0/8 (default) Mailbox size limit: 0 (default) Local address extension character: + (default) Internet protocols to use: all (default)
Explanation of /etc/postfix/main.cf
Only the non-debconf lines are explained. For much more, run
man 5 postconf or visit [1].
smtp_tls_loglevel=1
Basic logging of connections to smtp.gmail.com.
smtp_tls_security_level=encrypt
Require an encrypted TLS connection to smtp.gmail.com. It would be preferable to use the verify level, but this did not work.
smtp_sasl_auth_enable=yes
Enable SMTP authentication.
smtp_sasl_password_maps=hash:/etc/postfix/sasl/passwd
Where the SMTP authentication data is to be found.
smtp_sasl_security_options = noanonymous
This one is a bit obscure: by specifying noanonymous, one allows plaintext passwords to be sent (I think noplaintext is the next level "up" from noanonymous). Gmail's SMTP server apparently accepts plaintext authentication only.
smtp_generic_maps=hash:/etc/postfix/generic
Where the generic mapping data is to be found.
relayhost=[smtp.gmail.com]:587
Address and port number for SMTP connections. Putting the hostname in square brackets means it is interpreted as a hostname, rather than a mail name (as I understand it, Postfix uses "normal" DNS records rather than MX records when square brackets are used).
Explanation of /etc/fetchmailrc
Run man fetchmail for details. Fetchmail's configuration
language has the interesting property of ignoring some words (like
"with") and punctuation (like the comma and semicolon).
set syslog
Log messages to syslog; fetchmail messages will appear in /var/log/mail.log.
set daemon 240
Check for mail every 240 seconds.
poll pop.gmail.com
Each account entry starts with keyword "poll", followed by the server hostname.
with nodns,
This is probably unnecessary.
with protocol POP3
Connect to pop.gmail.com mail using the POP3 protocol.
user "[email protected]" there is jane here,
Login to the POP3 server with username "[email protected]"; deliver mail to local user "jane".
with password doeadeer,
The POP3 password is "doeadeer".
with ssl, sslcertck;
Use SSL in communicating to the POP3 server, and verify that the certificate is valid. fetchmail uses the certificates provided by the ca-certificates packages for this.
Verifying the Gmail SMTP server certificate
The configuration above does not verify the certificate of the Gmail SMTP server. This would be very easy to do but for Bug 118963 If you need this verification, you can either read reference 2 above, which shows you how to download and install the certificate yourself, or you can do something like this:
mkdir /var/spool/postfix/certs cp /etc/ssl/certs/* /var/spool/postfix/certs
Then, in main.cf, change the smtp_tls_security_level line and add an smtp_tls_CApath line as follows:
smtp_tls_security_level=verify smtp_tls_CApath=/certs
This might need to be redone if you upgrade postfix (e.g., when upgrading Ubuntu).
If Nothing Is Working
If possible, check that you can access the Gmail SMTP and POP3 services with a client like Thunderbird; Google provide complete instructions for setting up Thunderbird here. You can try port 465 instead of 587 for SMTP. You can do a check that SMTP connections can be made using stunnel, as follows:
stunnel -v 2 -c -n smtp -f -r smtp.gmail.com:587
You should see something like this:
2007.10.15 22:10:13 LOG5[9230:3083238176]: Using 'smtp.gmail.com.587' as tcpwrap per service name 2007.10.15 22:10:13 LOG5[9230:3083238176]: stunnel 3.26 on i486-pc-linux-gnu PTH READ+LIBWRAP with OpenSSL 0.9.8c 05 Sep 2006 220 mx.google.com ESMTP b30sm3913237ika 2007.10.15 22:10:15 LOG5[9230:3083238176]: VERIFY OK: depth=1, /C=ZA/ST=Western Cape/L=Cape Town/O=Thawte Consulting cc/OU=Certification Services Division/CN=Th awte Premium Server CA/[email protected] 2007.10.15 22:10:15 LOG5[9230:3083238176]: VERIFY OK: depth=0, /C=US/ST=Californ ia/L=Mountain View/O=Google Inc/CN=smtp.gmail.com
Terminate this connection with Ctrl-C. You can also try testing the POP3 connection, though I had no success with this:
stunnel -v 2 -c -n pop3 -f -r pop.gmail.com:995
Note that you cannot use openssl's s_client to test the SMTP connection; Gmail's SMTP server requires the client to begin communications with HELO (or EHLO), while s_client jumps straight to STARTTLS.
