I'm using the latest version of Plesk (18.0.24) and Smartermail (build 7242). It's a fresh install with migrated domains. When, in some cases, i try to activate the mail service and get this error (also in some cases when migrating):

Error: mailmng failed: Incorrect Content-Type: must be textual to extract_string, JSON to extract_json 

at newDomain(DOMAIN-EXAMPLE.com)(SmarterMail::Local::Provider::newDomain line 194)
at execute console command --add-domain(vconsoleapp::start line 93)
at execute "C:\Program Files (x86)\Plesk\admin\bin\mailmng" --add-domain "--domain-name=DOMAIN-EXAMPLE.com" "--disk-quota=524288000" "--total-disk-quota=26214400000"(vconsoleapp::run line 110)
(Error code 1)

I assume this is a Smartermail error? Any idea's what to do?

Regards,

Koen