Bukkit

1) Essentials: If you have "Protect all signs" set as "true".
From blXP config.yml set Block-Explosives to true.
This requires to stop server and change setting from config.yml, then restart server.

2) Essentials: If you have "creeper-blockdamage" set as "true".
From blXP config.yml set Block-Explosives to true.
This requires to stop server and change setting from config.yml, then restart server.

3) WorldGuard: If you have "block-tnt-block-damage" set as "true".
From blXP config.yml set Block-Explosives to true.
This requires to stop server and change setting from config.yml, then restart server.

4) WorldGuard: If you have "block-creeper-block-damage" set as "true".
From blXP config.yml set Block-Explosives to true.
This requires to stop server and change setting from config.yml, then restart server.