Delay in subscribing persistent messages with clean_session=False

[anudeep010291]

Mosquitto version : 1.6.4
MQTT protocol : v3.1
Environment : Ubuntu 18.04.6 LTS

There has been a delay in subscribing the messages that were received when the subscriber is down. The clean session is set to False in order to persist the messages and the following scenario has been tested.

The publisher publishes 100 messages every 15 sec to a particular topic during which the subscriber listening to the same topic has been down for ~15 minutes. After the subscriber is up it takes around 10 to 15 minutes to receive all the messages that were persisted in those 15 minutes it was down and then starts getting the live messages. Can any one help me out why this delay has been happening ?

Please do let me know if any details are required.

@SURAJTHEGREAT For your reference