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How to prevent auto-reply message to be sent multiple times when out-of-office is on

Situation:

1. Exchange Server sends an auto-reply to not@home.com
2. not@home.com sends an out-of-office autoreply to Exchange Server
3. Exchange Server sends again an auto-reply to not@home.com

In badly configured situation or deliberate attacks, this could lead to an infinite circle. I'd like to prevent step 3 from happening. Because auto-replies and out-of-office replies are not easily recognized from normal messages, I think we need some timer: do not send to same address when messages are received within, say, 5 minutes.

How can I configure Exchange Server 2007 for a particular common address?
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abel
Asked:
abel
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3 Solutions
 
Glen KnightCommented:
"How can I configure Exchange Server 2007 for a particular common address?" What do you mean by this?

You could just turn off external out of office?
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abelAuthor Commented:
With "common" I mean it's one of those addresses (directories, objects?) that everybody (with correct rights) can view. It is configured and maintained on the server. Sorry, I forgot the right term for this. It's the info@company address where all sales people can look into.

It should send the message "Thanks, we'll get in contact with you within an hour". But when the sending address has an OOO (out-of-office), I don't want a second thank-you note to be send.
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abelAuthor Commented:
I believe you call this a "public folder"?
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Glen KnightCommented:
I think you are refering to a shared mailbox?

There is no way to distinguish between the type of message you are being sent.
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abelAuthor Commented:
XS has many extensions and possibilities. It is even used for mailing lists. I need not distinguish between messages sent. I just need to prevent automatic messages sent twice to the same address.

Outlook (through XS) does the same: a typical out-of-office reply is sent only once to a recipient. I need that behavior for an auto-reply as well.
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Glen KnightCommented:
If you have an autoreply it will reply to all messages, that is by design.
As far as I am aware (unless you want to get into scripting) there is no way to prevent this.
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abelAuthor Commented:
This issue must have come up before, esp. to prevent cyclic mail attacks (where A >> B >> A >> B >>... etc).

If it cannot be configured, I wouldn't mind a script, plugin or something similar. Since it seems so common, I'd assume someone already invented the wheel. If not, can you help me inventing it? (sorry, not an XS expert anymore after 2000).
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Glen KnightCommented:
Sorry I cannot help with a script. Not a scripting person.

However I would suggest simply creating an Out of Office and then using a 3rd party tool like: http://www.symprex.com/products/out-of-office-extender/ which will reset the out of office every day so that if someone who sent a message yesterday sends one today or tomorrow they will still get the reply.

The downside is that they will only get one message a day.

Auto-Reply's are not ideal because of the problem you described.  There are possibly ways to do this server side with an Event Sink but again, auto-reply rules can cause mail loops and that's why they are not generally recommended.
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abelAuthor Commented:
Still looking for a few things here:

1) if it is not possible with the default Exchange Server (which I still doubt, it seems such an obvious feat), I like to see some documentation link about it.

2) the Symprex tools does some things, but is not what I'm looking for. I need either a plugin for Exchange Server, or someone who's done this already.

From what I read on the subject, it seems that Exchange Server tries its best already to prevent a mail loop. But how many mails does it need in a loop before it calls it a loop?
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Glen KnightCommented:
Exchange will not allow looping with it's default configuration so unless you have changed it then this will not happen.

I don't believe you can do what you are truing to do, you basically want to reply to every message the first time and then stop any replies to out of office?  Not possible.
On a plus side the out of office will only reply to you once (and not again until it has been turned off and back on again) so it kind of negates your requirement anyway.

However if you have an autoreply rule and someone at the other end has an autoreply rule on then this could cause a loop which is why auto-reply features are unreliable and not recommended.
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abelAuthor Commented:
Maybe I haven't made myself very clear, but:

An out-of-office already works just like that: only one message per sender. So it is possible.

An auto-reply replies to everything. But looping is prevented (but to what level?) which should prevent a re-reply of a full messagebox to be again replied by the XS. The looping you mention in your last paragraph doesn't seem to happen in real life. If it is not recommended, how do "real" auto-reply features work and with what software? In practice, most professional companies have them, so I find it hard to believe that it isn't possible.

I want a combination of the two: an auto-reply that only replies once to original messages. It is very well possible that the looping feature is preventing this already. But I need some definitive source on this so that I can hit the XS configurators about it.
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Glen KnightCommented:
The only way you are going to do it is with scripting or with a 3rd part tool.
Like this one: http://www.emailaddressmanager.com/outlook/auto-reply.html
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abelAuthor Commented:
But that's for Outlook. I need something for Exchange Server. This is a public address/folder managed on the XS level.
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Glen KnightCommented:
Not possible I am afraid.

You might also want to have a look at the comments here from TechSoEasy: http://www.experts-exchange.com/Networking/Network_Management/Q_22635839.html
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Alan HardistyCommented:
This is not possible natively in Exchange without some separate scripting or a 3rd Party Application (not that I know of one) as has already been advised by Demazter.  
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Jamie McKillopCommented:
Hello,

To accomplish what you want, first create a distribution group and asssign an addrees like no-reply@yourdomain.com to the distribution group. The membership of the group should be empty. Now go to the public folder and modify the rule. On the reply template, click Options then click Direct Replies To. Beside "have replies sent to" select the distribution group you created. You may want to modify the text of the auto-reply to indicate that replies to the auto-reply will not go to anyone. Save the template.

Now when a message comes into the public folder the auto-reply rule will fire but replies to the auto-reply will go to no-reply@yourdomain.com instead of back to the folder. When mail is sent to a distribution group with a blank membership Exchange just drops the message.

JJ
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Glen KnightCommented:
Thanks Alan!

jjmck > That will result in an NDR being sent to the person that sends the message back which if there is an auto rule on the other end will cause a reply and another NDR and another reply etc etc etc.

That is exactly what the author is trying to avoid.

abel > As I have told you repeatedly and has been confirmed by another of EE's top Exchange experts, this cannot be done natively with Exchange and your best bet is to implement a 3rd part autoresponder tool like the one I have offered.
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Jamie McKillopCommented:
No, it will not result in an NDR. When a message is sent to a distribution list with a blank membership, Exchange drops the message without sending an NDR.

It would work like this:

1. External sender sends a message to the public folder address
2. Public folder sends auto-reply back to external sender but message has a reply-to of non-reply@yourdomain.com
3. External sender auto-replies but auto-reply goes to no-reply@yourdomain.com
4. Exchange receives auto-reply and sees it goes to a distribution list without any members
5. Exchange silently drops message

JJ
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abelAuthor Commented:
Demazter, I know you told me repeatedly, the req. for att. was done long before that (during the silent time). The people I need to convince need some source and don't take it if it's "just a guy they don't know". However, it does help a lot that more people are drawing the same conclusions.

Still, I remain very surprised that no XS server plugin exists for this (you showed an Outlook plugin).

The tip of JJ is interesting. It also explains why so many "auto-generated mail" I receive has a no-reply in the reply-to field. It may be an option in our scenario. The NDR is easy enough to turn off for an individual address.

For a real solution, I think I have to get my hands dirty myself. I'm handy enough and in the good ol' days made some plugins for Exchange Server (pre-XS 2000). If this really doesn't exist on server level, why not create it and share it ;-)
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abelAuthor Commented:
I apparently typed while JJ was typing. So it's even simpler, no NDR is sent at all.

I'll mention this to the team. Thanks for the update, JJ.
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abelAuthor Commented:
While jjmck answered the question "how to prevent mail loops with auto-replies" with a working and simple-to-implement solution, I'm going to share the points. Demazter has been very patient in explaining me that it isn't trivial and that it cannot be done without a third-party application. While one wasn't found that worked directly with XS, it did show how untrivial this seemingly easy request was.

Thanks to all participating experts!
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abelAuthor Commented:
Thanks to all of you for helping with this tricky issue and thanks for a good workaround.
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