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Old 05-24-2014, 09:20 AM   #1
Registered: Aug 2012
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Understanding postfix log

I just sent an email using PHPMailer, and set setFrom, addReplyTo, and addAddress to (note that this question has nothing to do with PHPMailer, I just included this info on the rare case it will help). I have installed postfix.i686 2:2.6.6-6.el6_5 on Centos 6.5. I am trying to understand the /var/log/maillog log.

For instance, the first line "vps sendmail". I take it this is my server "vps" using command "sendmail". I thought I was using postfix, and not sendmail? Also, what is with the Authentication-Warning.

I also see that sendmail, postfix/smtpd, postfix/cleanup, postfix/qmgr are all being used. How are these related? (If this is two long of a question, please disregard)

Later I see a couple "Network is unreachable" lines. What is with these?

Thank you

May 24 08:56:18 vps sendmail[3797]: s4ODuIpF003797: Authentication-Warning: apache set sender to using -f
May 24 08:56:19 vps sendmail[3797]: s4ODuIpF003797:, size=12546, class=0, nrcpts=1, msgid=<>, relay=apache@localhost
May 24 08:56:21 vps postfix/smtpd[3952]: connect from localhost[]
May 24 08:56:21 vps postfix/smtpd[3952]: 2423E3350019: client=localhost[]
May 24 08:56:21 vps postfix/cleanup[3955]: 2423E3350019: message-id=<>
May 24 08:56:22 vps postfix/qmgr[1982]: 2423E3350019: from=<>, size=13172, nrcpt=1 (queue active)
May 24 08:56:22 vps sendmail[3797]: s4ODuIpF003797: to=John Doe <>, (48/48), delay=00:00:04, xdelay=00:00:01, mailer=relay, pri=42546, relay=[] [], dsn=2.0.0, stat=Sent (Ok: queued as 2423E3350019)
May 24 08:56:22 vps postfix/smtp[4035]: connect to[2001:558:fe2d:70::22]:25: Network is unreachable
May 24 08:56:22 vps postfix/smtp[4035]: connect to[2001:558:fe14:70::22]:25: Network is unreachable
May 24 08:56:22 vps postfix/smtp[4035]: 2423E3350019: to=<>,[]:25, delay=1.7, delays=1/0.01/0.42/0.21, dsn=2.0.0, status=sent (250 2.0.0 5pwR1o00o1yV1880KpwRLq mail accepted for delivery)
May 24 08:56:22 vps postfix/qmgr[1982]: 2423E3350019: removed
May 24 08:56:24 vps postfix/smtpd[3952]: disconnect from localhost[]
Old 05-24-2014, 10:13 AM   #2
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Regardless of whether sendmail, postfix, exim4, or some other MTA is used, the command to send mail on *nix is usually called sendmail for historical reasons. It does not mean that you're using sendmail as your MTA; you're using postfix as you thought.

System log messages tend to take a standard form: "timestamp hostname application/process-name-or-PID message". Why is the hostname included, you ask. It's because machines can send syslog messages to other machines for aggregation, and it's really helpful in that case to know which machine actually generated a log message.

I am not a Postfix wizard, so I don't know the specifics of how it works, but most MTAs usually have several daemons. Probably, smtpd is what actually listens for incoming port 25 connections annd services them while qmgr and cleanup actually manage the machine's internal mail queue. For example, if there's a transient delivery failure, the message will sit in an internal queue and something has to be responsible for attempting a redelivery or deleting it (and sending an error back to the user) if the system decides it can't be delivered.

As for the "network is unreachable" lines, it looks like your machine first attempts to use IPv6 to talk to the comcast mail servers (2001:558:fe2d:70::22 looks like an IPv6 address to me). Since your machine is probably not set up to use IPv6, this fails. It then switches back to using IPv4 (connecting to, which I'm assuming you've obfuscated because it's not a valid address), and that succeeds.
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Old 05-24-2014, 09:36 PM   #3
Doug G
Registered: Jul 2013
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Also you might grab an analyzer utility like pflogsumm (which I use to email me a daily mail server summary report). You can look at the report and then back at the maillog to gain some more insight how the report entries were generated from log entries.
Old 05-24-2014, 09:44 PM   #4
Registered: Feb 2013
Location: San Jose, CA
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'sendmail' is generally aliased, even in postfix systems.

I think btmiller might be right about the logs.

This article explains your auth warning:


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