diff --git a/docs/configuring-playbook-bot-postmoogle.md b/docs/configuring-playbook-bot-postmoogle.md
index bbbfa405..680365e4 100644
--- a/docs/configuring-playbook-bot-postmoogle.md
+++ b/docs/configuring-playbook-bot-postmoogle.md
@@ -47,8 +47,8 @@ ansible-playbook -i inventory/hosts setup.yml --tags=setup-all,start
 
 ## Usage
 
-To use the bot, invite the `@postmoogle:DOMAIN` into a room you want to use as a mailbox, after that send `mailbox NAME` to enable email address `NAME@matrix.domain` and start receiving emails
+To use the bot, invite the `@postmoogle:DOMAIN` into a room you want to use as a mailbox, after that send `!pm mailbox NAME` to enable email address `NAME@matrix.domain` and start receiving emails
 
-Send `help` to the room to see the bot's help menu for additional commands.
+Send `!pm help` to the room to see the bot's help menu for additional commands.
 
 You can also refer to the upstream [documentation](https://gitlab.com/etke.cc/postmoogle).
diff --git a/roles/matrix-bot-postmoogle/defaults/main.yml b/roles/matrix-bot-postmoogle/defaults/main.yml
index 7d5818ce..4679e678 100644
--- a/roles/matrix-bot-postmoogle/defaults/main.yml
+++ b/roles/matrix-bot-postmoogle/defaults/main.yml
@@ -73,7 +73,10 @@ matrix_bot_postmoogle_password: ''
 matrix_bot_postmoogle_homeserver: "{{ matrix_homeserver_container_url }}"
 
 # Command prefix
-matrix_bot_postmoogle_prefix: ''
+matrix_bot_postmoogle_prefix: '!pm'
+
+# Max email size in megabytes, including attachments
+matrix_bot_postmoogle_maxsize: '1024'
 
 # Sentry DSN
 matrix_bot_postmoogle_sentry: ''
diff --git a/roles/matrix-bot-postmoogle/templates/env.j2 b/roles/matrix-bot-postmoogle/templates/env.j2
index f9f49e79..d2662fd3 100644
--- a/roles/matrix-bot-postmoogle/templates/env.j2
+++ b/roles/matrix-bot-postmoogle/templates/env.j2
@@ -6,6 +6,7 @@ POSTMOOGLE_PORT={{ matrix_bot_postmoogle_port }}
 POSTMOOGLE_DB_DSN={{ matrix_bot_postmoogle_database_connection_string }}
 POSTMOOGLE_DB_DIALECT={{ matrix_bot_postmoogle_database_dialect }}
 POSTMOOGLE_PREFIX={{ matrix_bot_postmoogle_prefix }}
+POSTMOOGLE_MAXSIZE={{ matrix_bot_postmoogle_maxsize }}
 POSTMOOGLE_SENTRY={{ matrix_bot_postmoogle_sentry }}
 POSTMOOGLE_LOGLEVEL={{ matrix_bot_postmoogle_loglevel }}
 POSTMOOGLE_NOENCRYPTION={{ matrix_bot_postmoogle_noencryption }}