Emails over 15Mbs fail on IOS FW

Unanswered Question
Mar 15th, 2007


I have a Cisco 1841 providing internet access with FW and NAT.

The customer has an Exchange server on the internal network. When they send emails with attachments over 15Mbs in size they fail. Emails with attachments under this size are fine.

They have also removed the C1841 and replaced it with a non-cisco firewall and emails were fine.

Does anyone know what on the IOS FW would cause this? Would one of the inspection rules be causing the problem?

Any advice/help would be appreciated.



I have this problem too.
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thomas.chen Wed, 03/21/2007 - 08:21

First thing you can try is in regard of CBAC set the default size to 20Mb or more. Following document may help you regarding it

As a last option you may remove the inspection to see if this fixes your problem. Use following command for this

no ip inspect name DEFAULT100 smtp


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