# Introduction
`BLP` is a command introduced with [MSNP2](../versions/msnp2.md).

It is a Notification Server command, without either a request or response payload.

It modifies if messages sent to you by users not on your Allow List (AL) are allowed to be received.

# Client/Request
`BLP TrID [ AL | BL ]`

# Server/Response
`BLP TrID listVersion [ AL | BL ]`

Where `listVersion` is the new List Version.

# Examples

## Setting to AL (Allow messages by default)
```
C: BLP 1 AL
S: BLP 1 255 AL
```

## Setting to BL (Block messages by default)
```
C: BLP 2 BL
S: BLP 2 256 BL
```

## Invalid argument
*NOTE: This is an assumption. The actual error code here is unknown.
It may also lead to an Instant Disconnection.*
```
C: BLP 3 CL
S: 201
```

# Known changes
* [MSNP10](../versions/msnp10.md) and higher: List Versions are dropped in `ABCHMigrated: 1` mode.
* Removed in MSNP13. You get instantly disconnected if you try using the command.