Exchange 2010 Receive Connector TARPIT, DelayedACK, Slow Delivery internal E-Mail

by butsch 10. October 2013 16:15


You see following in the Logs under:

C:\Program Files\Microsoft\Exchange Server\V14\TransportRoles\Logs\ProtocolLog\SmtpReceive\

2013-09-24T17:09:35.723Z,SBSERVER2\Windows SBS Internet Receive SBSERVER2,08D072FC7C4ACF6A,21,,,*,Tarpit for '0.00:00:00.312' due to 'DelayedAck',Delivered


You have following problem:

Submitting a message to a Exchange 2007/2010/2013 is significantly slower than expected. This problem does not occur when submitting messages to other types of mail servers, including earlier versions like Exchange 2003.


Why this happens:

Sometimes end customers hang a Small Business with Exchange 2007/2010 direct into the internet without a SPAM appliance or MX-Filter.

Because of that Microsoft has limited most of the Receive Connector settings. Spammers often drop connection if they see that a MX endpoint

Reacts slowly. This is additional to "Grey Listing" a method MS uses to prevent spam out of the box. It clearly does not replace a SPAM Filter but

Prevents worst maybe for Small Business customers who have limited knowledge in Exchange Configuration.


If you have a front located MX-record filter which as example is provide by you ISP/HOSTING Company and you ONLY receive incoming E-mail

Direct through that single IP from the provider (Filtered by the Provider) you can turn those values for that specific Relay-Connector off.


Here is how to read the VALUES from all receive Connector on your Exchange

get-ReceiveConnector | select name,tarpitinterval, maxacknowledgementdelay


Default settings on Small Business Server Exchange 2010:

TarpitInterval         : 00:00:05

MaxAcknowledgementDelay     : 00:00:30


Disabling the tarpit interval

Set-receiveconnector "internal_relay" -tarpitinterval 00:00:00

Disabling MaxAcknowledgement delay

Set-receiveconnector " internal_relay " -maxacknowledgementdelay 0




Exchange 2007 | Exchange 2010

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