PrivateMessages integrates with PlaceholderAPI plugin. You can display other plugins data inside of messages (lang.yml) , at this point it is possible with following messages: MESSAGE_TO_FORMAT, MESSAGE_FROM_FORMAT, MESSAGE_TO_OFFLINE_FORMAT

Other than that, PrivateMessages brings its own placeholders which can be used anywhere:

• %privatemessages_last_message_sender% – returns player’s last messsage sender’s name (only during current server session)
• %privatemessages_last_message_recipient% – returns number of messages player has received when offline and still not marked as read by executing /pmclear command
• %privatemessages_unread_messages_count% – returns number of messages player has received when offline and still not marked as read by executing /pmclear command
• %privatemessages_message_notification_sound_number% – returns identification number of sound selected for incoming messages to player
• %privatemessages_message_notification_sound_enabled% – returns true when player has enabled incoming messages sound
• %privatemessages_spy_enabled% – returns true when player has spy mode enabled
• %privatemessages_messages_enabled% – returns true when player has enabled sending/receiving private messages
• %privatemessages_tips_enabled% – returns true when player has enabled receiving plugin tips
• %rel_privatemessages_messages_exchanged% – relational placeholder; returns number of all messages sent between two given players
• %rel_privatemessages_player_ignored% – relational placeholder; returns true when player passed as second argument is ignored by player passed as first argument – this makes checks within PrivateMessages plugin only, doesn’t look for other plugins’ ignores e.g. Essentials’ ignores, even when PrivateMessages integrates with this plugin