Memory leak

I frequently leave my laptop on for many days. Just put it to standby by closing the lid. Today I noticed that xfce4-mailwatch-plugin takes quite a chunk of RAM:

Uptime is around one week:

$ uptime
 20:58:51 up 6 days, 10:49,  1 user,  load average: 2,98, 2,12, 1,73