We just upgraded to FOSS 7.1.3 and since then, evry few hours, zimbra stops sending/receiving mail. zmcontrol status shows:
antispam Running
antivirus Stopped
zmclamdctl is not running
ldap Stopped
logger Stopped
zmlogswatchctl is not running
mailbox Stopped
mysql.server is not running.
zmmailboxdctl is not running.
memcached Stopped
memcached is not running.
mta Stopped
postfix is not running
zmsaslauthdctl is not running
snmp Stopped
zmswatch is not running.
spell Stopped
zmapachectl is not running
stats Stopped
zmconfigd Stopped
zmconfigd is not running.
I look in /var/logs/zimbra.log and see this when zimbra is not running:
Nov 10 23:20:43 mail postfix/postfix-script[8529]: fatal: the Postfix mail system is not running

This is from /opt/zimbra/log/mailbox.log:
2011-11-09 00:02:55,002 WARN [ImapSSLServer-23] [name=**Emailaddress*;mid=3;ip=166.137.15.198;ua=iP hone Mail/9A334;] imap - ignoring error during UID FETCH:
com.zimbra.cs.mailbox.MailServiceException: No such blob: mailbox=3, item=1001491, change=1324327
ExceptionId:ImapSSLServer-23:1320814975002:1ce72a976f85698e
Code:mail.NO_SUCH_BLOB
at com.zimbra.cs.mailbox.MailServiceException.NO_SUCH _BLOB(MailServiceException.java:269)
at com.zimbra.cs.mailbox.MailItem.getBlob(MailItem.ja va:971)
at com.zimbra.cs.mailbox.MessageCache.fetchFromStore( MessageCache.java:224)
at com.zimbra.cs.mailbox.MessageCache.getMimeMessage( MessageCache.java:160)
at com.zimbra.cs.mailbox.Message.getMimeMessage(Messa ge.java:427)
at com.zimbra.cs.imap.ImapMessage.getMimeMessage(Imap Message.java:225)
at com.zimbra.cs.imap.ImapHandler.fetch(ImapHandler.j ava:3359)
at com.zimbra.cs.imap.ImapHandler.doFETCH(ImapHandler .java:3179)
at com.zimbra.cs.imap.ImapHandler.executeRequest(Imap Handler.java:425)
at com.zimbra.cs.imap.TcpImapHandler.processCommand(T cpImapHandler.java:111)
at com.zimbra.cs.tcpserver.ProtocolHandler.processCon nection(ProtocolHandler.java:199)
at com.zimbra.cs.tcpserver.ProtocolHandler.run(Protoc olHandler.java:140)
at java.util.concurrent.ThreadPoolExecutor$Worker.run Task(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run (ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)

Also see this a little below the above error:
2011-11-10 23:20:23,989 WARN [main] [] misc - Could not establish a connection to the database. Retrying in 5 seconds.
com.zimbra.common.service.ServiceException: system failure: getting database connection
ExceptionId:main:1320985223988:6ad84f444451f1a2
Code:service.FAILURE
at com.zimbra.common.service.ServiceException.FAILURE (ServiceException.java:248)
at com.zimbra.cs.db.DbPool.getConnection(DbPool.java: 314)
at com.zimbra.cs.db.DbPool.getConnection(DbPool.java: 278)
at com.zimbra.cs.db.DbPool.waitForDatabase(DbPool.jav a:200)
at com.zimbra.cs.db.DbPool.startup(DbPool.java:191)
at com.zimbra.cs.util.Zimbra.startup(Zimbra.java:157)
at com.zimbra.cs.util.Zimbra.startup(Zimbra.java:123)
at com.zimbra.soap.SoapServlet.init(SoapServlet.java: 128)
at javax.servlet.GenericServlet.init(GenericServlet.j ava:241)
at org.mortbay.jetty.servlet.ServletHolder.initServle t(ServletHolder.java:440)
at org.mortbay.jetty.servlet.ServletHolder.doStart(Se rvletHolder.java:263)
at org.mortbay.component.AbstractLifeCycle.start(Abst ractLifeCycle.java:50)
at org.mortbay.jetty.servlet.ServletHandler.initializ e(ServletHandler.java:685)
at org.mortbay.jetty.servlet.Context.startContext(Con text.java:140)
at org.mortbay.jetty.webapp.WebAppContext.startContex t(WebAppContext.java:1254)
at org.mortbay.jetty.handler.ContextHandler.doStart(C ontextHandler.java:517)
at org.mortbay.jetty.webapp.WebAppContext.doStart(Web AppContext.java:471)
at org.mortbay.component.AbstractLifeCycle.start(Abst ractLifeCycle.java:50)
at org.mortbay.jetty.handler.HandlerCollection.doStar t(HandlerCollection.java:152)
at org.mortbay.jetty.handler.ContextHandlerCollection .doStart(ContextHandlerCollection.java:156)
at org.mortbay.component.AbstractLifeCycle.start(Abst ractLifeCycle.java:50)
at org.mortbay.jetty.handler.HandlerCollection.doStar t(HandlerCollection.java:152)
at org.mortbay.component.AbstractLifeCycle.start(Abst ractLifeCycle.java:50)
at org.mortbay.jetty.handler.HandlerWrapper.doStart(H andlerWrapper.java:130)
at org.mortbay.component.AbstractLifeCycle.start(Abst ractLifeCycle.java:50)
at org.mortbay.jetty.handler.HandlerWrapper.doStart(H andlerWrapper.java:130)
at org.mortbay.jetty.handler.DebugHandler.doStart(Deb ugHandler.java:127)
at org.mortbay.component.AbstractLifeCycle.start(Abst ractLifeCycle.java:50)
at org.mortbay.jetty.handler.HandlerWrapper.doStart(H andlerWrapper.java:130)
at org.mortbay.jetty.Server.doStart(Server.java:224)
at org.mortbay.setuid.SetUIDServer.doStart(SetUIDServ er.java:158)
at org.mortbay.component.AbstractLifeCycle.start(Abst ractLifeCycle.java:50)
at org.mortbay.xml.XmlConfiguration.main(XmlConfigura tion.java:985)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Nativ e Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Native MethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(De legatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.mortbay.start.Main.invokeMain(Main.java:194)
at org.mortbay.start.Main.start(Main.java:534)
at org.mortbay.start.Main.start(Main.java:441)
at org.mortbay.start.Main.main(Main.java:119)
Caused by: com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientC onnectionException: Could not create connection to database server. Attempted reconnect 3 times. Giving up.