“Out of memory; check if mysqld or some oth er process uses all available memory;” error

[Amarnath Shivashankar]

We have found that the MYSQL on all Email DB servers starts throwing "Out of
memory; check if mysqld or some other process uses all available memory;"
error. The error goes once we restart MySQL. But after a week again the same
problem occurs. We have 4 GB of physical memory on the server but Mysql
utilizes only up to 2.5 GB & starts throwing Out of memory error

Please help me to resolve this.........