Fedora8, Intel motherboard, 4GB memory, Zimbra OSS 5.0.0. Worked well from the moment of installation version 5.0.0. I have updated Zimbra to version 5.0.11 and have received regular stops mailboxd in 15-20 minutes after start. Manipulations with parameter mailboxd_java_heap_memory_percent have not given any changes.
After a stop there is an error in mailboxd.log:
FATAL [LmtpServer-2]  system - Fatal error occurred while handling connection java.lang is fixed.
OutOfMemoryError: Java heap space at org.apache.lucene.store. IndexInput.readString (IndexInput.java:111)
...etc... lot of Java errors....
How to eliminate the stop reasons? Now I have temporarily corrected it, restarting zmmailboxdctl each 15 minutes through crontab.