fsesperf.dll is a fsesperf
belonging to F-Secure Anti-Virus® E-Mail Scanning
from F-Secure Corporation
Non-system processes like fsesperf.dll originate from software you installed on your system. Since most applications store data in your system's registry, it is likely that your registry has suffered fragmentation and accumulated invalid entries which can affect your PC's performance. It is recommended that you check your registry to identify slowdown issues.