Enable remote mailslots
This `DWORD` value controls server-side support for remote mailslots through the Computer Browser service.
since 0.9.8.11
Purpose
Show registry keys (1)
HKLM\Software\Policies\Microsoft\Windows\Bowser\EnableMailslots
This DWORD value controls server-side support for remote mailslots through the Computer Browser service. A value of 0 disables this functionality.
Remote mailslots are a deprecated mechanism for one-way interprocess communication over a network. They transmit datagram messages to a particular computer or broadcast them to multiple computers in a domain. This setting affects the SMB server's mailslot functionality; it does not generally disable SMB file sharing.
Notes
Security
The Remote Mailslot Protocol provides no authentication or authorization mechanisms of its own. Setting the value to 0 makes this obsolete, unauthenticated communication channel unavailable.
Microsoft classifies remote mailslots as insecure, unreliable, and deprecated. They are therefore disabled by default in current Windows releases.
Possible side effects
After remote mailslots are disabled, the Computer Browser service no longer operates as expected for functionality that depends on them. Legacy applications or components that receive messages through remote mailslots can no longer use that form of network communication.
This setting does not necessarily disable every form of network discovery. Its effect is limited to functionality that actually depends on the Computer Browser service and remote mailslots.
Notes
Microsoft maps this device-scoped value to the Enable remote mailslots Group Policy setting under Network > Lanman Server. 0 means disabled and 1 means enabled. Windows must be restarted before a change takes effect.
The policy reference lists the setting for Windows 11 version 24H2, build 26100.3613, and later. Remote mailslots are also disabled by default beginning with Windows Server 2025 and are deprecated.
Microsoft documentation
Microsoft Learn: LanmanServer Policy CSP – EnableMailslots
Microsoft Learn: SMB security hardening – SMB Remote Mailslots deprecation