Today I just got an announcement from Wietse Venema (the developer of Postfix) via Postfix mailing list that Postfix 2.7.0 stable has been released. An on-line version of this announcement will be available at http://www.postfix.org/announcements/postfix-2.7.0.html.

For the past several releases, the focus has moved towards improving the code and documentation, and updating the system for changing environments.

Below are the new improvements and features available in Postfix 2.7.0 stable version:

- Improved before-queue content filter performance. With “smtpd_proxy_options = speed_adjust”, the Postfix SMTP server receives the entire message before it connects to a before-queue content filter. Typically, this allows Postfix to handle the same mail load with fewer content filter processes.

- Improved address verification performance. The verify database is now persistent by default, and it is automatically cleaned periodically, Under overload conditions, the Postfix SMTP server no longer waits up to 6 seconds for an address probe to complete.

- Support for reputation management based on the local SMTP client IP address. This is typically implemented with “FILTER transportname:” actions in access maps or header/body checks, and mail delivery transports in master.cf with unique smtp_bind_address values.

- The postscreen daemon (a zombie-blocker in front of Postfix) is still too rough for a stable release, and will be made “mature” in the Postfix 2.8 development cycle (however you can use Postfix 2.7 with the Postfix 2.8 postscreen and dnsblog executables and master.cf configuration; this code has already proven itself).

No functionality has been removed, but it is a good idea to review the RELEASE_NOTES file for the usual minor incompatibilities or
limitations.

You can find Postfix version 2.7.0 at the mirrors listed at http://www.postfix.org/

The same code is also available as Postfix snapshot 2.8-20100213. Updated versions of Postfix version 2.6, 2.5 and perhaps earlier
will be released with the same fixes that were already included with Postfix versions 2.7 and 2.8.

The conventional way for a mail client program to send e-mail is using TCP port 25, which is also the port used by mail servers to talk to each other. But port 25 is now widely abused by malware to spread worms and spam. As a result, many ISPs are restricting its use.
There is another method to send e-mail which is more preferred than using port 25. Its name is mail or message submission that using TCP port 587.
Detail explanation taken from Wikipedia:

Message submission (RFC 2476) and SMTP-AUTH (RFC 2554) were introduced in 1998 and 1999, both describing new trends in e-mail delivery. Originally, SMTP servers were typically internal to an organization, receiving mail for the organization from the outside, and relaying messages from the organization to the outside. But as time went on, SMTP servers (Mail transfer agents), in practice, were expanding their roles to become message submission agents for Mail user agents, some of which were now relaying mail from the outside of an organization. (e.g. A company executive wishes to send e-mail while on a trip using the corporate SMTP server.) This issue, a consequence of the rapid expansion and popularity of the World Wide Web, meant that the SMTP protocol had to include specific rules and methods for relaying mail and authenticating users to prevent abuses such as unsolicited e-mail (spam) relaying.

In fact almost all mail server supports mail submission port 587 but it may not be turned on. That is why I write this tutorial to let you know how to enable or activate the mail submission in Postfix.
By default the mail submission in Postfix is already there. You just need to enable it on /etc/postfix/master.cf file. So open that file using your text editor and edit to be like below:

1
2

smtp      inet  n       -       n       -       -       smtpd
submission inet n       -       n       -       -       smtpd

Then restart the postfix service.

$ sudo /etc/init.d/postfix restart

or

$ sudo /usr/sbin/postfix reload

Now in your mail client program, change the SMTP port to 587. In Thunderbird should be like below:

Then try to send an e-mail using TCP port 587. If failed, double check the master.cf file and also look at the /var/log/maillog file.

You want to log email Subject field into /var/log/maillog?

By default the email subject field is not logged to the maillog file. To log it, here is the trick.

Edit /etc/postfix/main.cf and uncomment  the option below:

header_checks = regexp:/etc/postfix/header_checks

In the ‘/etc/postfix/header_checks’ file, write the line below in one line:

/^Subject:/ WARN

Then reload the postfix service using “postfix reload”

Tail the maillog file, you should see some logs similar like below:

Oct 26 18:32:28 mx-1 postfix/smtpd[7532]: 8C7255798B: client=unknown[xxx.xx.31.166], sasl_method=LOGIN, sasl_username=user@mydomain.com
Oct 26 18:32:28 mx-1 postfix/cleanup[6701]: 8C7255798B: warning: header Subject: Room Rate - Weatherford Company from unknown[xxx.xx.31.166]; from= to= proto=ESMTP helo=
Oct 26 18:32:28 mx-1 postfix/cleanup[6701]: 8C7255798B: message-id=<0CFA5E16DE5D67499273CF31D3949F7201B5FA0C@MEEXCH01.wft.root.loc>
Oct 26 18:32:28 mx-1 postfix/qmgr[19610]: 8C7255798B: from=, size=70837, nrcpt=1 (queue active)

Ref: http://www.irbs.net/internet/postfix/0410/2142.html

SMTP Authentication is a scheme which was introduced in 1999 by J. Myers of Netscape Communications and finally released as RFC 2554 (“SMTP Service Extension for Authentication”). It is partly based on the SMTP Service Extensions as defined in RFC 1869.
Using SMTP Authentication activated both on server and client, you can send email from anywhere, everywhere, even from mars. As long as authenticated, you can relay access to the smtp server.
However, there are some softwares or application which does not support SMTP Authentication like Mailman mailing list manager. If you send an email to the mailing list, the sender will be detected as “mailinglistname-bounces@yourdomain.com”. This email address is not a valid account so Mailman will not be authenticated to send your email and ‘Relay access denied’ will be logged.
The only way to solve this problem is by bypassing the SMTP Auth and here are how to bypass the SMTP Auth on Postfix (My email server is using Postfix as the MTA). We will allow relay access based-on ip address.

a. Edit /etc/postfix/main.cf and insert list of ip addresses or in CIDR format to ‘mynetworks’ option. On my case, allowing Mailman to relay to localhost (127.0.0.1/32). You can add some other ip addresses as needed.

mynetworks = 127.0.0.1/32, 203.153.xx.xx/29, 203.153.xxx.xxx/32

b. Still in the main.cf, put ‘permit_mynetworks’ value in the first order of ‘smtpd_recipient_restrictions’. You must set it in the first order, otherwise Relay access denied will be logged. Here is mine:

smtpd_recipient_restrictions = permit_mynetworks, permit_sasl_authenticated,
                                reject_unauth_destination,
                                reject_non_fqdn_recipient,
                                reject_invalid_hostname,
                                reject_unauth_destination,
                                reject_unknown_sender_domain,
                                reject_unknown_recipient_domain,
                                reject_rbl_client sbl.spamhaus.org,
                                reject_rbl_client dnsbl.ahbl.org,
                                reject_rbl_client dnsbl.njabl.org,
                                reject_rbl_client dnsbl.sorbs.net,
                                reject_rbl_client cbl.anti-spam.org.cn,
                                check_policy_service unix:postgrey/socket,
                                permit

c. Reload postfix and test to send email without smtp authentication from the networks/ip addresses you have specified in ‘mynetworks’ above to domains other than the domains that already registered in your mail server.

Your email should be sent and no ‘Relay access denied’ logged.

If an email message is undeliverable, it will bounce back with ‘MAILER-DAEMON’  telling you that the message could not be delivered to the destination addresses. The queue will try to keep delivering based on your mail server configuration. Unfortunately it will make your mail server takes some resources to the queues. And we dont want this thing happened.

In this example, we want to delete all ‘MAILER-DAEMON’ email queues. Using this trick you can free your mail server from ‘MAILER-DAEMON’ queues at that time. Below is the command:

for i in `postqueue -p|grep 'MAILER-DAEMON' |awk {'print $1'}|grep -v 'MAILER-DAEMON'`; do postsuper -d $i ; done

To delete all queues, simply use ‘postsuper -d ALL’ command.
Hope this trick useful for you.