How do I reset admin password in management console? Can it be done via email of admin user?

That depends which platform your MC is installed on.

On Windows

1. Open Services (Win + R, “services.msc”) and stop “Resilio Connect Server” service
2. Open elevated Command Prompt (run it as Admin) and navigate to 
    C:\Program Files\Resilio Connect Server
3. Run command 
    srvctrl.cmd resetpassword <username> --appdata <path>
   where path is MC's storage folder. 
   Depending on service's Logon type, it will be either 
    C:\Windows\System32\config\systemprofile\AppData\Roaming\resilio-connect-server or 
    C:\Windows\ServiceProfiles\LocalService\AppData\Roaming\resilio-connect-server
4. Start “Resilio Connect Server” service and go by the link suggested in command output.

On Linux

1. Stop Management Console 
    ./srvctrl stop command
2. Reset password with
    ./srvctrl resetpassword <username> --appdata <path> 
    where path is the directory where srvctrl is installed. 
3. Start server with ./srvctrl start and open the link from command output

More info is here: https://connect.resilio.com/hc/en-us/articles/115001080284-How-to-reset-admin-password

Just in case you CAN login into Management Console (or still logged in) you can change password in Settings -> Users -> (select user) -> Edit