To reset the SnappyMail admin password, you need to SSH to your server, and then modify the following file:
Comment out the following line
admin_password = 'password' to ;admin_password = 'password'
Note that the symbol semicolon (;) to comment that line
Exit and save the file and then reboot your server.
Open the SnappyMail admin panel area to make the SnappyMail generating admin password. Visit the admin area using the following URL format (E.g: https://IPSERVER:8090/snappymail/?admin)
Next, SSH again to your server and then open the following file to get the new generated password for your SnappyMail admin.
Do not forget to change the password in the panel after logging in.
Hope this helps.