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exchange 2013 receive connector reject

Posted on 2015-01-01
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Last Modified: 2015-01-07
Hi.
I am getting the following warning in my exchange 2013 error logs:

Receive connector Internet Connector HFC-EKHAT rejected an incoming
connection from IP address 1xx.2xx.1xx.1xx.
The maximum number of connections per source (20)
for this connector has been reached by this source IP address.


This appears constantly in the logs.  This is incoming from a country that we don't usually send or receive mails from often.

Is this normal or could this point to something more sinister?

Thanks.
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Question by:fijiboy
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by:Gareth Gudger
ID: 40527028
Sounds like someone is trying to perform some sort of denial of service attack. It sounds like Exchange is your first hop. Do you have any kind of message hygiene software, appliance or cloud service in front of your Exchange server? If not, I'd recommend it.
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by:fijiboy
ID: 40527123
Thanks Gareth. We currently do not have a service in front of our email server apart from our corporate firewall. Am looking at some security for email security etc. Is there something I can do hardware the server in the meanwhile? They seem to be connecting on port 25.
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Gareth Gudger earned 500 total points
ID: 40527249
A temporary solution may be to block that IP at your firewall. But they will often change IPs so this is a temporary solution at best.

If you have the Edge Transport role in your environment you could also do an IP Block List Provider - might help.
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