We're using Zimbra Beta M2 on RHEL 4 (kernel 2.6.9-11.EL)
Yesterday we saw the following in zimbra.log and the server stopped responding:

~100 lines like this:
2006-02-02 23:43:06,340 INFO [http-443-Processor90] [mid=20;ip=x.x.x.x;name=x@x.com;] FileBlobStore - deleting blob 17216 in mailbox 20

and then:
2006-02-02 23:43:19,302 FATAL [http-443-Processor90] [mid=20;ip=x.x.x.x;name=x@x.com;] system - handler exception
java.lang.OutOfMemoryError: Java heap space

Output from ps -ef|grep tomcat:
/opt/zimbra/jdk1.5.0_05/bin/java -Xms455m -Xmx455m -client -XX:NewRatio=2

When it crashed, the server was running for about a month. It has ~100 users & processes ~2000s messages/day.

The box has 1.5Gb of memory. Do you think, the heap size should be increased? Any reason to believe it's a memory leak?

Let me know if you need more info.