diff --git a/local/lib/python3/cmk/base/plugins/agent_based/mailcow_mailboxes.py b/local/lib/python3/cmk/base/plugins/agent_based/mailcow_mailboxes.py
index 8eebb78..18f9f0c 100644
--- a/local/lib/python3/cmk/base/plugins/agent_based/mailcow_mailboxes.py
+++ b/local/lib/python3/cmk/base/plugins/agent_based/mailcow_mailboxes.py
@@ -93,12 +93,16 @@ def parse_mailcow_mailboxes_section(string_table):
         display_name = line[4]
         # number of messages within mailbox
         number_of_messages = int(line[5])
-        # percent in use, rounded to full percent
-        percent_in_use = int(line[6])
         # calculate storage used for all messages in mailbox
         quota = int(line[7])
-        total_number_of_bytes_used = int(line[8])
-        percent_storage_used_for_messages = total_number_of_bytes_used * 100 / quota
+        if quota == 0:
+            # quota is not set, if this is the case, line[6] contains no numeric value, but the char "-"
+            percent_in_use = 0
+        else:
+            total_number_of_bytes_used = int(line[8])
+            percent_storage_used_for_messages = total_number_of_bytes_used * 100 / quota
+            # percent in use, rounded to full percent
+            percent_in_use = int(line[6])
         # get time of last login for IMAP/POP3/SMTP (seconds since epoch)
         last_imap_login = int(line[9])
         last_pop3_login = int(line[10])
diff --git a/mkp/Mailcow-1.1.3.mkp b/mkp/Mailcow-1.1.3.mkp
new file mode 100755
index 0000000..0ee707e
Binary files /dev/null and b/mkp/Mailcow-1.1.3.mkp differ