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Home » Kerio User Forums » Kerio Connect » Switch off "Disposition-Notification-To" (switch off all automatic delivery notifications)
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saco

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I saw a lot spammers use the "Disposition-Notification-To" to confirm a valid email address.

How to prevent the server to send such automatic mails from Kerio to the spammer (and all others !)
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MarkK

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That would be going against the RFC specifications, but with spam today it would be nice to have some sort of spam checking take place before anything is acknowledged.

Are you using the spam repellent time delay option? That may help with some of those since it delays Connect from fully handshaking the communication until the delay expires. Many spam servers will quit after a short bit in an effort pump out as many as they can.
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Pavel Dobry (Kerio)

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saco wrote on Thu, 03 December 2015 12:31
I saw a lot spammers use the "Disposition-Notification-To" to confirm a valid email address.

How to prevent the server to send such automatic mails from Kerio to the spammer (and all others !)


Well, this email is created by email client, not by server.
It cannot be disabled in Kerio Connect Client. But it can in Outlook and others.

I would say you can try to use new message filter feature in Kerio Connect 9 to completely remove "Disposition-Notification-To" email header from incoming messages (eg. with sender different from your domain): http://kb.kerio.com/product/kerio-connect/server-configurati on/filtering-messages-on-the-server-1831.html

[Updated on: Thu, 03 December 2015 18:30]


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MarkK

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Pavel (kerio),

But at what point does the new filtering take place? Is it before the server processes the new email and its headers? The link you provided does not really indicate that.

If 9.0 does process the mail headers first when it is received, then it will follow the RFC specs and still send the delivery notification. Yes, the new 9.0 server side filters could then take an action based on the headers, but saco was wanting to prevent that automatic notification from happening. I'm not sure if the spammer getting a good delivery notification first from the server, followed by a server based - header based rules generated bad delivery notification would really have any affect.
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Pavel Dobry (Kerio)

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MarkK wrote on Thu, 03 December 2015 19:12
Pavel (kerio),

But at what point does the new filtering take place? Is it before the server processes the new email and its headers? The link you provided does not really indicate that.

If 9.0 does process the mail headers first when it is received, then it will follow the RFC specs and still send the delivery notification. Yes, the new 9.0 server side filters could then take an action based on the headers, but saco was wanting to prevent that automatic notification from happening. I'm not sure if the spammer getting a good delivery notification first from the server, followed by a server based - header based rules generated bad delivery notification would really have any affect.


Well, DSN (delivery receipt) is processed after the rules, when the email reaches destination mailbox. BUT "Disposition-Notification-To" is not a delivery receipt. It is a read receipt request - and this is processed by an email client when you actually open and read the email.

[Updated on: Thu, 03 December 2015 19:40]


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MarkK

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Quote:
"Disposition-Notification-To" is not a delivery receipt. It is a read receipt request


My mistake on mixing those up. Thanks for pointing that out.
Nice to know when the DSN is processed in the cycle though. Thanks!
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