HELP! ... Unable to add new domains

[energylevel]

I'm getting this error when I try to add a new domain, any ideas please?:

Failed domain creation: Unable to update domain data: Failed mail post-configuration: Can't create mail domain servie: mailManager->addDomain() failed: mailmng failed: Invalid class string (COM Error 800401F3) at execute console command --add-domain
---------------------- Debug Info -------------------------------
0: D:\SWsoft\Plesk\admin\htdocs\domains\create_domain.php:160