Unable to connect local SmarterMail to Plesk Obsidian: Integration error: Incorrect Content-Type: must be textual to extract_string

Symptoms

• Unable to connect local SmarterMail to Plesk Obsidian at Tools & Settings > Server Components > Mail Server > SmarterMail Server 100.xx. The following error is shown:

  PLESK_ERROR: "Integration error: Incorrect Content-Type: must be textual to extract_string, JSON to extract_json. at getVersion()(SmarterMail::Common::Provider::getVersion line 22)"
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• SmarterMail was installed on the server before Plesk.
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Cause

The default http://localhost:9998/ binding is missing in SmarterMail site in IIS (Windows > IIS > Sites > SmarterMail > Bindings)

The default link to the SmarterMail web interface on a dashboard and Start menu by default is http://localhost:9998/. That is why Plesk requires that local SmarterMail must be accessible by URL http://localhost:<port>/.

Resolution

Add the missing binding:

1. Connect to the server via RDP

2. Go to IIS > Sites > SmarterMail > Bindings and add the binding on port 9998 specifying the 'localhost' as a hostname:
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3. Click OK.

4. Log in to Plesk

5. Connect the local SmarterMail at Tools & Settings > Server Components > Mail Server > SmarterMail Server 100.xx