Admins can define global settings for archiving channels and deleting messages. You need "Manage system settings" to configure global chat settings.

Configure settings

1. Go to Administration > System settings > Messaging 
2. Activate Automatically archive channels or Automatically remove old private messages.
3. Specify the number of hours after which a channel is archived or a message deleted. This indicates how many hours have passed since the last message was posted in the channel, or how many hours have passed since the original message was posted before they are deleted.
4. Optionally, under Advanced settings, enter the schedule for archiving channels or deleting messages. You need to specify the timing using a cron pattern.  By default, the cron 0 0 * * * * is defined, which means the job runs every hour
5. Select Save to update the settings. The settings will take effect immediately and will also affect past messaging history.

We recommend informing your users about the archiving and deletion timeframes, so they are aware that their channels can be archived and their messages can be deleted. 

When you delete old messages, they and any transferred files are completely deleted from the database. Similarly, archived group channels are effectively deleted and cannot be found and restored.