Rejecting uknown email addresses during SMTP transaction

M

macconnect

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Joined
Jan 8, 2007
Messages
17
Spam backscatter is a HUGE problem these days. Does the stock DA mail configuration support rejecting messages for invalid local addresses during the SMTP transaction?

Having to accept messages and discard them is a lousy way of dealing with the problem.
 
Unless you've changed your exim.conf file, DA won't accept email if the local user doesn't exist.

Jeff
 
It will accept a message for an over quota account and bounce it back later though. Very annoying.

Matt
 
I always thought it kept it in the queue until there was room. Are you sure it's not doing that?

Jeff
 
jlasman said:
I always thought it kept it in the queue until there was room. Are you sure it's not doing that?

Jeff
Click to expand...

You are absolutely right. It keeps it in the queue then bounces it after 5 days. If they were over there ~50M quota its usually not gonna change in 5 days. Usually it means they have not bothered to check it in months or they have there client setup to leave messages on the server.

Matt
 
I hate to bring up this old thread, but is this still the case? Does Exim accept mail and then bounce later? If so does this give me the Backscatter that I am reading about now?

Thanks,
Phil
 
If the mailbox is full, DirectAdmin WILL accept the email and hold it in the queue.

Generally this is desired so if the user complains that the mailbox is full, the admin won't have to tell the user that he's lost his mail.

However once the mail has been accepted then the server must try to return it if it cannot deliver it.

Other behavior might be to send a temporary failure, telling the sending server the mailbox is full. I'm inclined to think it's better behavior, but I'm not sure how to implement it.

If it's possible, do you think that it should be the default behavior?

Jeff

Jeff
 
jlasman said:
If the mailbox is full, DirectAdmin WILL accept the email and hold it in the queue.

Generally this is desired so if the user complains that the mailbox is full, the admin won't have to tell the user that he's lost his mail.

However once the mail has been accepted then the server must try to return it if it cannot deliver it.

Other behavior might be to send a temporary failure, telling the sending server the mailbox is full. I'm inclined to think it's better behavior, but I'm not sure how to implement it.

If it's possible, do you think that it should be the default behavior?

Jeff
Click to expand...

Yes, a temp failure would be much better than holding it for 4 days to just return it. Like it was said above in this post, if a users mailbox is full I doubt they are going to empty it in time for the mail to be delivered anyway. I think some of the big providers do the temp fail thing and tell you to retry your sending later.

/Phil
 
See my last post in the other thread, about postmaster & abuse email, and also see if you can figure out how to do the temp failure if mailbox is full... instead of putting email into queue. If someone else can point me to some documentation it'll save me some valuable time and get the changes into exim.conf more quickly.

Anyone?

Thanks!

Jeff
 
jlasman said:
See my last post in the other thread, about postmaster & abuse email, and also see if you can figure out how to do the temp failure if mailbox is full... instead of putting email into queue. If someone else can point me to some documentation it'll save me some valuable time and get the changes into exim.conf more quickly.

Anyone?

Thanks!

Jeff
Click to expand...

This is the best info I could find so far:

Q0712: I've hacked sendmail to make an ioctl call at the time of the SMTP RCPT command, to check if a user has exceeded their email quota. If they have I issue a temporary failure and a message - can I do this with Exim?

A0712: If you can make this happen in Perl you can use the embedded Perl facility, and use it from a condition condition in an ACL statement. You can also use the expansion facility to run an external program, but this uses more resources because it uses another process.
Click to expand...
 
DirectAdmin already maintains exim.pl for the spam filtering. I don't know how to use it for temp failure on full mailbox. If someone else has done it and you can google it, we can move forward from there.

Jeff
 
There is an interesting article here about preventing exim from sending backscatter:

http://www.timj.co.uk/linux/rcpt-time-quota-maildir.php

This sounds like it would address the issue of rejecting messages for accounts that are over quota but alas my exim skills are more than a little rusty. Someone that possesses deeper magic than me might be able to adapt this. Might also be able to make the rejection be a tempfail so that the sending mailserver retries later.
 
DirectAdmin uses multiple virtual mailbox directories; I'll look into this as I have time.

Jeff
 
I have something that should work, but our main office management system is having problems and I can't do anything further until I have a successful rebuild.

Note to others: we're having major problems with latest versions of kde4 and kontact, and our systems have always been build on kontact and scripting. If I can't get it fixed by the end of this weekend I'll have to work on developing another back-office solution.

Jeff
 
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