Posts Tagged ‘MTA’

How to redirect / forward all postfix emails to one external email address?

Thursday, October 29th, 2020

Postfix_mailserver-logo-howto-forward-email-with-regular-expression-or-maildrop

Lets say you're  a sysadmin doing email migration of a Clustered SMTP and due to that you want to capture for a while all incoming email traffic and redirect it (forward it) towards another single mailbox, where you can review the mail traffic that is flowing for a few hours and analyze it more deeper. This aproach is useful if you have a small or middle sized mail servers and won't be so useful on a mail server that handels few  hundreds of mails hourly. In below article I'll show you how.

How to redirect all postfix mail for a specific domain to single external email address?

There are different ways but if you don't want to just intercept the traffic and a create a copy of email traffic using the always_bcc integrated postfix option (as pointed in my previous article postfix copy every email to a central mailbox).  You can do a copy of email flow via some custom written dispatcher script set to be run by the MTA on each mail arriva, or use maildrop filtering functionality below is very simple example with maildrop in case if you want to filter out and deliver to external email address only email targetted to specific domain.

If you use maildrop as local delivery agent to copy email targetted to specifidc domain to another defined email use rule like:

if ( /^From:.*domain\.com/:h ) {
  cc "!someothermail@domain2.com"
}


To use maildrop to just forward email incoming from a specific sender towards local existing email address on the postfix to an external email address  use something like:

if ( /^From: .*linus@mail.example.com.*/ )
{
        dotlock "forward.lock" {
          log "Forward mail"
          to "|/usr/sbin/sendmail linuxbox@collector.example.com"
        }
}

Then to make the filter active assuming the user has a physical unix mailbox, paste above to local user's  $HOME/.mailfilter.

What to do if your mail delivered via your Email-Server.com are sent from a monitoring and alarming scripts that are sending towards many mailboxes that no longer exist after the migration?

To achive capturing all normal attempted to be sent traffic via the mail server, we can forward all served mails towards a single external mail address you can use the nice capability of postfix to understand PCRE perl compatible regular expressions. Regular expressions in postfix of course has its specific I recommend you take a look to the postfix regexp table documentation here, as well as check the Postfix Regex / Tester / Debugger online tool – useful to validate a regexp you want to implement.

How to use postfix regular expression to do a redirect of all sent emails via your postfix mail relayhost towards external mail servers?

 

In main.cf /etc/postfix/main.cf include this line near bottom or as a last line:

virtual_maps = hash:/etc/postfix/virtual, regexp:/etc/postfix/virtual-regexp

One defines the virtual file which can be used to define any of your virtual domains you want to simulate as present on the local postfix, the regexp: does load the file which is read by postfix where you can type the regular expression applied to every incoming email via SMTP port 25 or encrypted MTA ports 385 / 995 etc.

So how to redirect all postfix mail to one external email address for later analysis?

Create file /etc/postfix/virtual-regexp

/.+@.+/ external-forward-email@gmail.com

Next build the mapfile (this will generate /etc/postfix/virtual-regexp.db )
 

# postmap /etc/postfix/virtual-regexp

This also requires a virtual.db to exist. If it doesn't create an empty file called virtual and run again postmap postfix .db generator

# touch /etc/postfix/virtual && postmap /etc/postfix/virtual


Note in /etc/postfix/virtual you can add your postfix mail domains for which you want the MTA to accept mail as a local mail.

In case you need to view all postfix defined virtual domains configured to accept mail locally on the mail server.
 

$ postconf -n | grep virtual
virtual_alias_domains = mydomain.com myanotherdomain.com
virtual_alias_maps = hash:/etc/postfix/virtual


The regexp /.+@.+/ external-forward-email@gmail.com applied will start forwarding mails immediately after you reload the MTA with:

# systemctl restart postfix


If you want to exclude target mail domains to not be captured by above regexp, in /etc/postfix/virtual-regexp place:

/.+@exclude-domain1.com/ @exclude-domain1.com
/.+@exclude-domain2.com/ @exclude-domain2.com

Time for a test. Send a test email


Next step is to Test it mail forwarding works as expected
 

# echo -e "Tseting body" | mail -s "testing subject" -r "testing@test.com" whatevertest-user@mail-recipient-domain.com

Get daily E-Mail Reports statistics on postfix Linux mail server

Tuesday, July 14th, 2020

https://pc-freak.net/images/Postfix-email-server-logo.svg-1

I've had today a task at work to monitor a postfix mail send and received emails (MAIL FROM / RPCT TO) and get out a simple statistics on what kind of emails are coming and going out from the Postfix SMTP on a server?

Below is shortly explained how I did it plus you will learn how you can use something more advanced to get server mail count, delivery status, errors etc. daily.
 

1. Using a simple script to process /var/log/messages

For that I made a small script to do the trick, the script simply checks mail delivery logged information from /var/log/maillog process a bit sort and logs in a separate log daily.

#!/bin/sh
# Process /var/log/maillog extract from= and to= mails sort
# And log mails to $LOGF
# Author Georgi Georgiev 14.07.2020

DATE_FORM=$(date +'%m_%d_%y_%H_%M_%S_%h_%m');
LOG='/home/gge/mail_from_to-mails';
LOGF="$LOG.$DATE_FORM.log";
CUR_DATE=$(date +'%m_%d_%y_%T');
echo "Processing /var/log/maillog";
echo "Processing /var/log/maillog" > $LOGF;
echo >>$LOGF
echo "!!! $CUR_DATE # Sent MAIL FROM: addresses: !!!" >> $LOGF;
grep -E 'from=' /var/log/maillog|sed -e 's#=# #g'|awk '{ print $8 }'|sed -e 's#<# #g' -e 's#># #g' -e 's#\,##'|sort -rn|uniq >> $LOGF;

echo "!!! $CUR_DATE # Receive RCPT TO: addresses !!!" >>$LOGF;
grep -E 'to=' /var/log/maillog|sed -e 's#=# #g'|awk '{ print $8 }'|sed -e 's#<# #g' -e 's#># #g' -e 's#\,##'|sort -rn|uniq >> $LOGF;


You can get a copy of the mail_from_to_collect_mails_postfix.sh script here.

I've set the script to run via a crond scheduled job once early in the mornthing and I'll leave it like that for 5 days or so to get a good idea on what are the mailboxes that are receiving incoming mail.

The cron I've set to use is as follows:

# crontab -u root -l 
05 03 * * *     sh /home/gge/mail_from_to.sh >/dev/null 2>&1

 

This will be necessery later for a Email Server planned migration to relay its mail via another MTA host.

 

2. Getting More Robust Postifx Mail Statistics from logs


My little script is of course far from best solution to get postfix mail statistics from logs.

If you want something more professional and you need to have a daily report on what mails sent to mail server and mails sent from the MTA to give you information about the Email delivery queue status, number of successful and failed emails from a mail sender / recipient and a whole bunch of useful info you can use something more advanced such as pflogsumm perl script to get daily / weekly monthly mail delivery statistics.

What can pflogsumm do for you ?

 

 

Pflogsumm is a log analyzer/summarizer for the Postfix MTA. It is
designed to provide an overview of Postfix activity, with just enough
detail to give the administrator a “heads up” for potential trouble
spots and fixing any SMTP and email related issues.

Pflogsumm generates summaries and, in some cases, detailed reports of
mail server traffic volumes rejected and bounced email and server
warnings, errors, and panics.

At the time of writting this article it is living on jimsun.linxnet.com just in case if pflogsumm.pl's official download location disappears at some time in future here is pflogsumm-1.1.3.tar.gz mirror stored on pc-freak.net

– Install pflogsumm

Use of pflogsumm is pretty straight forward, you download unarchive the script to some location such as /usr/local/bin/pflogsumm.pl  add the script executable flag and you run it to create a Postfix Mail Log statistics report for you

wget http://jimsun.linxnet.com/downloads/pflogsumm-1.1.3.tar.gz -O /usr/local/src/pflogsumm-1.1.3.tar.gz

 

# mkdir -p /usr/local/src/
# cd /usr/local/src/
# tar -zxvf pflogsumm-1.1.3.tar.gz
# cd pflogsumm-1.1.3/

# mv /usr/local/pflogsumm-1.1.3/pflogsumm.pl /usr/local/bin/pflogsumm
# chmod a+x /usr/local/bin/pflogsumm


That's all, assuming you have perl installed on the system with some standard modules, we're now good to go: 

To give it a test report to the command line:

# /usr/local/bin/pflogsumm -d today /var/log/maillog

pflogsumm-log-summary-screenshot-linux-received-forwarded-bounced-rejected

To generate mail server use report and launch to some email of choice do:

# /usr/local/bin/pflogsumm -d today /var/log/maillog | mail -s Mailstats your-mail@your-domain.com


To make pflogsumm report everyday various interesting stuff such as (message deferrals, message bounce, details, smtp delivery failures, fatal errors, recipients by message size etc. add some cronjob like below to the server:

# /usr/sbin/pflogsumm -d yesterday /var/log/maillog | mail -s Mailstats | mail -s Mailstats your-mail@your-domain.com

If you need a GUI graphical mail monitoring in a Web Browser, you will need to install a webserver with a perl / cgi support,  RRDTools and MailGraph.

linux-monitoring-mail-server-with-mailgraph.cgi

How to configure Exim to relay mail to remote SMTP server on Debian and Ubuntu

Wednesday, August 24th, 2011

I’m required to do some mail relaying on a Debian Linux host which should use a remote mail server to relay its mails.
Until so far I’ve had not much experience with exim as I prefer using qmail, whever a mail server is needed. However since now only a relaying was necessery and exim is the default installed MTA on Debian, I’ve decided to use exim to take care of the SMTP mail relaying.
After a bit of reading it happened configuring exim to relay via remote SMTP server is more than easy!

All I had to do is run the command:

debian-relay:~# dpkg-reconfigure exim4-config

Next in the Ncruses interface to appear:

Debian Exim relay smtp config screenshot

I had to choose the option:

mail sent by smarthost; no local mail

Next a dialog appears asking for:
System mail name:
Therein it’s necessery to type in the hostname of the remote SMTP to be used for mail relay.
Next dialog asks for:
IP-addresses to listen on for incoming SMTP connections:
and I left it with 127.0.0.1 however if exim is supposed to be visible from external network one might decide to put in real IP address there.

Pressing OK leads to the next dialog:
 Other destinations for which mail is accepted: 
I decided to leave this blank as I don’t want to accept mail for any destinations.
Next pane reads:
Visible domain name for local users:
I’ve typed inside my smtp relay server e.g.:
smtp.myrelaymail.com

Further comes:
IP address or host name of the outgoing smarthost:
There once again I typed my mail relay host smtp.relaymail.com

The next config screen is:
Keep number of DNS-queries minimal (Dial-on-Demand)?
On any modern Linux host the default answer of No is fine.
Following prompt asked if I want to:
Split configuration into small files?
I’ve decided not to tamper with it and choosed No
Afterwards mail relaying works like a charm thx God 😉