You receive an error in ESVA web interface, or you have recurrent cluster errors.
Error executing query: Table ‘maillog’ is marked as crashed and last (automatic?) repair failed.
This error can happen when you ran out of disk space in your ESVA VM or after a brute force shutdown of ESVA VM (e.g. power outage).
Since Libra Esva 3.5 release there is a handy tool to check and recover databases automatically.