This is the problem:
An intermittent 403 error on SMartermail or website is most frequently caused by the visitor exceeding the Dynamic IP Restrictions defined in the Internet Information Services (IIS) Manager.

By default the Dynamic  IP Restrictions are configured as follows in IIS:
Deny IP addresses based on the number of concurrent requests
Maximum number of concurrent requests: 10
Deny IP addresses based on the number of requests over a period of time
Maximum number of requests: 100

Any time that an IP address exceeds these limits the visitor will receive a 403 error until their number of connections to the site is reduced.

Here is the solution:
To help prevent the intermittent 403 errors increase the Dynamic IP Restrictions at the server level as follows:
  • Login to the server via Remote Desktop
  • open the Internet Information Services (IIS) Manager
  • Click the Server Name > IP Address and Domain Restrictions > Edit Dynamic Restriction Settings
  • Deny IP addresses based on the number of concurrent requests: Maximum number of concurrent requests: 100
  • Deny IP addresses based on the number of requests over a period of time: Maximum number of requests: 300

Article ID: 1156, Created On: 1/24/2021, Modified: 1/24/2021

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