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Messages Not Delivered or Delayed with Cisco Appliance

Messages Not Delivered or Delayed with Cisco Appliance(s)

Messages to my users are being delayed, or not delivered at all. There is a Cisco firewall, router, or switch in my environment. What is causing this issue?


For our customers using Cisco networking appliances, we suggest that the SMTP fixup or ESMTP inspection settings be disabled on your appliance prior to setting up your Email Protection service.

These settings have been known to be related to undelivered or delayed inbound and outbound messages.

For information on these settings and how to make changes, please see the links below:

3rd Party Blog - Cisco ASA Disable ESMTP Inspection:

Cisco Security Appliance (PIX 500 series, ASA 5500 series) Inspect Command Reference:

Cisco PIX 6.3 Configuring Application Inspection (Fixup):

Cisco Catalyst 6500 Series Switch and 7600 Series Router Firewall - Configuring Application and Protocol Inspection:

Microsoft TechNet - You Cannot Send or Receive E-Mail Messages Behind a Cisco PIX Firewall:

Please note that making any configuration changes to your networking appliances can have wide-reaching consequences. Please consult your organization's change control procedures before altering any settings.
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