OpenEMM & Greylisting

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christian.lang
Posts: 30
Joined: Thu Apr 19, 2007 3:24 pm

OpenEMM & Greylisting

Post by christian.lang » Fri Nov 30, 2007 10:39 am

Hello,
I have tried to find out how OpenEMM handels Softbounces which are caused by the so called Greylisting.

For those who don't know that Greylisting is: If you try to deliver a mail the first (few) times the recipient's mailserver will reject it with a temporary failure. In most cases the message tells you that this was caused by Greylisting, but that depends on the implementation.
A correctly implemented mailserver then tries to resend the email later on and after some tries the recipient's server will accept the message because because you tried to resend the message, it assumes that this is a "normal email" and no spam. Some Greylisting implementations also keep some records of successful deliveries and would deliver an email within the first try in a future mailing.

Now in case of rejects many Mailservers give quite different responses (except the part that all of them are temporary errors):
For example:
"dsn=4.3.0, stat=Deferred: 451 <nobody@greylistinghost.com>: Recipient address rejected: Greylisted"
"dsn=4.2.0, stat=Deferred: 450 <nobody@othergreylistinghost.com>: Recipient address rejected: Greylisted, please try again later!"


What i now tried to find out is how OpenEMM handles these reponse-codes in regards of the softbounce-functionalities.
As far as I could find out Softbounces in many cases are listed in the bounce_tbl and are therefore considered in the softbounce.sh/softbounce.py. If there are enough of these bounces (softbounces on 7 emails within a period 180 days as far as i know) it _seems_ to me that OpenEMM therefore would unsubscribe the User then. Because a successful delivery is not tracked by OpenEMM (as also stated by one of the developers here: http://www.openemm.org/forums/viewtopic.php?t=418) and therefore doesn't reset the Softbounce-Stats the result for for Users affected by Greylisting could be that they are unsubscribed even tough they have received all previous emails.

Has anyone had a deeper look on these matters and could clarify if I am so far right with my assumptions?
Is there any idea how to improve this process? Even if there is no full mailtracking in my opinion it might be an idea just do delete previous softbounces by a specific user on a successful delivery.

best regards,

Christian

ud
Posts: 141
Joined: Thu Aug 17, 2006 9:56 am
Location: Munich, Germany
Contact:

Post by ud » Thu Dec 06, 2007 11:13 am

Your understanding of the bounce handling is correct. As every mailserver seems to handle graylisting in its own way, there is no simple solution. If you have a look in the update.py script, there is already a simple catch to ignore graylisting soft bounces, but it does not catch all cases. This part could be improved, however.

-- ud

christian.lang
Posts: 30
Joined: Thu Apr 19, 2007 3:24 pm

...

Post by christian.lang » Thu Dec 06, 2007 11:54 pm

Thank you for your reply.
I haven't noticed before that there is a clause in the update.py which scans for "grey" and "gray" in die Status-Text Field.
In my opinion a long lasting solution can only be to track successfully delivered mails and to delete previous softbounces then - but as you wrote this is not a simple solution ...

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