Sendmail: how to restrict delivery based on "to" or "from"? Post: 302569565

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Top Forums UNIX for Advanced & Expert Users Sendmail: how to restrict delivery based on "to" or "from"? Post 302569565 by lupin..the..3rd on Monday 31st of October 2011 06:29:56 PM

10-31-2011

Registered User

Sendmail: how to restrict delivery based on "to" or "from"?

Hello,

I manage a large sendmail server that handles more than 20,000 pieces of mail per day. It's a bit unusual in that all this mail is only being sent to and from 4 local accounts. (It's an automated transaction processing system, whereby users submit a transaction via email attachment). I've got Sendmail configured to use Procmail for local delivery. My Procmail recipe then calls Cyrus Deliver for final message delivery into my Cyrus IMAP database. The four local mail accounts exist only within the Cyrus IMAP database, they are not unix user accounts on the system.

My problem is that Sendmail, when it receives a piece of incoming mail, has no way of determining if it's addressed to a valid account or not. It simply hands the mail to Procmail and lets procmail sort it out. Unfortunately, if someone makes a typo in the destination address, procmail simply drops the mail into a black hole and the person who submitted it never knows what happened!

For example, lets say one of my mail accounts is named Process@mydomain.com. If someone accidentally sends the mail to Lrocess@mydomain.com he does not receive any kind of rejection notice. Sendmail gladly accepts the message, hands it to Procmail for delivery, and then Procmail delivers it into an errors folder.

My understanding is that invalid account rejection should happen at the Sendmail level. How do I implement this in Sendmail? Here is the local delivery portion of my Sendmail.cf file:

# Cyrus Mailer using Procmail
Mprocmail, P=/usr/bin/procmail, F=lsDFMnPqA5@, S=10, R=20/40, T=X-Unix,
U=cyrus:mail,
A=procmail -p /etc/procmail/procmail.global CYRUSUSER=$u

I want Sendmail to call Procmail only for the four valid local accounts. For all other incoming mail, I want Sendmail to automatically bounce it back to the sender with an appropriate "invalid recipient" message.

Does anyone know how to do this? Thank you

Last edited by lupin..the..3rd; 10-31-2011 at 07:35 PM..

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LEARN ABOUT MINIX

mail

MAIL(1) 						      General Commands Manual							   MAIL(1)

NAME

       mail - send and receive electronic mail

SYNOPSIS

       mail [-dpqrv] [-f file] [user]

OPTIONS

       -d     Force use of the shell variable MAILER

       -f     Use file instead of /usr/spool/mail/user as mailbox

       -p     Print all mail and then exit

       -q     Quit program if SIGINT received

       -r     Reverse print order, i.e., print oldest first

       -v     Verbose mode

EXAMPLES

       mail ast 	   # Send a message to ast

       mail		   # Read your mail

DESCRIPTION

       Mail  is  an  extremely simple electronic mail program.	It can be used to send or receive email on a single MINIX system, in which case it
       functions as user agent and local delivery agent.  If the flag MAILER is defined in mail.c, it can also call a transport  agent	to  handle
       remote mail as well.  No such agent is supplied with MINIX.

       When  called  by  user  with no arguments, it examines the mailbox /usr/spool/mail/user, prints one message (depending on the -r flag), and
       waits for one of the following commands:

	 <newline> Go to the next message
	 -	   Print the previous message
	 !command  Fork off a shell and execute command
	 CTRL-D    Update the mailbox and quit (same as q)
	 d	   Delete the current message and go to the next one
	 q	   Update the mailbox and quit (same as CTRL-D)
	 p	   Print the current message again
	 s [file]  Save message in the named file
	 x	   Exit without updating the mailbox

       To send mail, the program is called with the name of the recipient as an
       argument.  The mail is sent, along with a postmark line containing the date.
       For local delivery, a file named after the recipient in the directory
       /usr/spool/mail must be writable.

       If the directory /usr/spool/mail does not exist then the mail is
       dumped on the console, so that system programs have a way to notify
       a user on a system that does not have a mail spool.

																	   MAIL(1)