You may have noticed that Eximstats database on your cPanel server is consuming more space (few GBs). This database stores the information about email delivery as well as it is being used to calculate bandwidth usage by POP3, IMAP. In most cases, it requires to keep last 30 days data in the database for the bandwidth calculation.
In the previous cPanel versions, the default setting was keeping 90 days data and this requires more space to keep the records for 90 days. As of 18.104.22.168 version the default value was set back to 30 days however if you are already running with 90 days settings, it will not change this setting back to 30 days in order to avoid data loss for this database. In this case, you can change this setting manually.
You can verify this settings from your WHM. You can see this settings at following in your WHM:
Tweak Settings >> Stats and Logs >> The interval, in days, to retain Exim stats in the database
If you have 90 days, you can reduce the days as per your requirement. Please note that if you have millions of records, it is not recommended that you reduce it directly to 30 days because once you change this settings, it will perform “delete” query in all tables to keep last 30 days data and this may overload your server if you have millions of records. It is recommended that you reduce the day gradually i.e. 80 days then 70 days then 60 days etc.
Note: You may have read from other source to reduce Eximstats database size by deleting all rows from phpMyAdmin however this is not recommended. If you delete all rows from Eximstats database, it will not count your bandwidth use for POP, IMAP etc. It is better you adjust this setting from WHM.