We have plesk with smarter mail.
Smarter mail functions independently of plesk at the admin level. Yes you can create user account in plesk and they show up in SM, but the actual admin account for SM is not defined or managed through plesk... not that i found yet.
you should be able to log into SM the same way you would on a stand alone. yourdomain:9998 (domain:port) or IP:9998, and then use the admin username and password to log in.
www.HawaiianHope.org - Providing technology services to non profit organizations, low income families, homeless shelters, clean and sober houses and prisoner reentry programs. Since 2015, We have refurbished over 11,000 Computers !