Traffic from the Intranet and External sources triggering the Jira UrlHostnameMismatchException

[Frank Koch]

We have traffic going to Jira on our Intranet and from an external portal that connects to Jira on the Intranet. The internal traffic has no issues, but traffic from the external portal triggers the UrlHostnameMismatchException error.

[[ DIAGNOSTICS: FAILED com.atlassian.gadgets.dashboard.internal.diagnostics.UrlHostnameMismatchException: Detected URL hostname, 'jira.intranet.com', does not match expected hostname, 'portal.external.com' ]]

We are using NGINX for our reverse proxy.

The Base URL is: https://jira.intranet.com/

Here's the regular link vs the link the portal creates.

https://jira.intranet.com/secure/Dashboard.jspa
https://portal.external.com/https/jira.intranet.com/secure/Dashboard.jspa

How so I accept traffic from both locations without triggering the UrlHostnameMismatchException error?