Skip to main content

CHECKRECIPIENT - Check Recipients during SMTP

IndiMail has a feature called CHECKRECIPIENT which allows indimail to check at SMTP, if the recipient to whom the mail is being addressed exists. It is always better to reject such users at SMTP rather than later during the actual delivery to the mailbox. Due to spam, in most of the cases, the Return Path will be forged or undeliverable. Hence you will be left with a condition where plenty of bounces will be left on your system, impacting the performance of your messaging system.

CHECKRECIPIENT can be also be used to reject mails for inactive users, overquota users and users who do not have the privilege to receive mails. CHECKRECIPIENT can be enabled by setting the environment variable CHECKRECIPIENT to one of the following values
  1. Reject the user if not present in IndiMail's MySQL database
  2. Reject the user if not present in IndiMail's MySQL database and recipients.cdb
  3. Reject user if not present in recipients.cdb
You can selectively turn on CHECKRECIPIENT for selective domains by including those domains (prefixing the domain with '@' sign) in the control file /etc/indimail/control/chkrcptdomains.

If the environment variable MAX_RCPT_ERRCOUNT is set qmail-smtpd will reject an email if in a SMTP session, the number of such recipients who do not exist, exceed MAX_RCPT_ERRCOUNT.

CHECKRECIPIENT also causes the RCPT TO command to be delayed by 5 seconds for every non-existent recipient, to make harvesting of email addresses difficult.

If you do not have large number of users

% su # echo 1 > /service/qmail-smtpd.25/variables/CHECKRECIPIENT # svc -d /service/qmail-smtpd.25 # svc -u /service/qmail-smtpd.25 # exit %

Post a Comment

Popular posts from this blog

IndiMail Installation for newbies in < 10 steps

Installing Indimail using YUM/APT Repository Install OS
openSUSE Leap 42.3
openSUSE Leap 42.2
openSUSE 13.2
openSUSE 13.1
SUSE Linux Enterprise 12 SP2
SUSE Linux Enterprise 12 SP1
SUSE Linux Enterprise 12
Red Hat
Feodra 27
Fedora 26
Red Hat Enterprise Linux 7
Red Hat Enterprise Linux 6
CentOS 7
CentOS 6
Debian 8.0
Debian 7.0
Ubuntu 17.04
Ubuntu 16.10
Ubuntu 16.04
Ubuntu 14.04
Ubuntu 12.04
Click the below URL for Install Instructions Shutdown MySQL if already running and disable MySQL from being started up by the system % /etc/init.d/mysqld stop % sudo chkconfig mysqld off % /bin/rm -f /service/mysql.3306/down
Start IndiMail
% sudo service indimail start Check Servicess
% sudo /usr/bin/svstat /service/* /service/clamd: up (pid 1014) 2985 seconds /service/dnscache: up (pid 1021) 2985 seconds /service/fetchmail: down 2985 seconds /service/freshclam: up (pid 1020) 2…

The AdminClient Protocol

IndiMail provides close to around 300 different programs as part of a flexible Enterprise Messaging Platform. You can carry administer the entire platform with around 45 of these programs. A program called indisrvr(8) provides a way for users to secure execute these commands from any remote location. To execute these programs, you need to have an admin account on the IndiMail server. These accounts can be created by the mgmtpass(8) program. Once you have an admin account on the IndiMail server, you can further restrict users to certain programs using the vpriv(8) program. vpriv can further modify privileges by allowing only certain options within a allowed program.

To execute these programs on the IndiMail server, you need to connect to port 4000 and use the adminclient protocol. The adminclient protocol is described below by showing a conversation between a client and the server 'indisrvr'

s - denotes server
c - denotes client

        s: "Login: "
        c: "u…

Writing Filters for IndiMail

IndiMail provides multiple methods by which you can intercept an email in transit and modify the email headers or the email body. A filter is a simple program that expects the raw email on standard input and outputs the message text back on standard output. The program /bin/cat can be used as a filter which simply copies the standard input to standard output without modifying anything. Some methods can be used before the mail gets queued and some methods can be used before the execution of local / remote delivery.

It is not necessary for a filter to modify the email. You can have a filter just to extract the headers or body and use that information for some purpose. IndiMail also provides the following programs - 822addr(1), 822headerfilter(1), 822bodyfilter(1), 822field(1), 822fields(1), 822header(1), 822body(1), 822headerok(1), 822received(1), 822date(1), 822fields(1) to help in processing emails.

Let us say that we have written a script /usr/local/bin/myfilter. The myfilter program …