Blocking user after multiple failed login attempts
It is possible to configure WebMail Pro so that user will be locked out and won't be able to login upon multiple failed login attempts, they would get an error message of the following kind:

The feature is enabled by setting the following option to true in data/settings/modules/Core.config.json
file:
"EnableFailedLoginBlock": [
false,
"bool"
],
NB: If your configuration file doesn't have such an option, try pressing "Update configuration" button in Database Settings screen of admin interface.
Please note that user access is blocked from their current IP address. They can still try logging into the WebMail Pro installation from another location.
The same configuration file also holds two more options for fine-tuning this functionality:
"LoginBlockAvailableTriesCount": [
3,
"int"
],
"LoginBlockDurationMinutes": [
30,
"int"
]
These settings control a number of failed login attempts, and block duration in minutes, respectively.