Well guys, I'm stuck.
Woke up this morning with my Zimbra server "running", but not delivering any mail. The web gui is up, but when someone tries to send mail via the web gui, it hangs. Furthermore, the mail server isn't forwarding any mail either.

zmcontrol status gave me:
Code:
 Host xxxxxxxxxxxxxxxxxxxx
       antispam                Running
        antivirus               Running
        ldap                    Running
        logger                  Running
        mailbox                 Stopped
                zmmailboxdctl is not running.
        mta                     Running
        snmp                    Running
        spell                   Running
        stats                   Running
        zmconfigd               Running
I then tried zmmailboxdctl start
Code:
Starting mailboxd...failed.
tail -f /opt/zimbra/log/mailbox.log shows plenty of normal activity, but also major Java crashes like:
Code:
INFO  [qtp1259286773-122:https://10.0.0.10:443/service/soap/SendMsgRequest] [name=user@domain.com;mid=32;ip=24.179.12.253;ua=Zimbra Desktop/7.1.4_11299_Windows;] SoapEngine - handler exception
com.zimbra.common.service.ServiceException: system failure: Unable to send message
ExceptionId:qtp1259286773-122:https://10.0.0.10:443/service/soap/S...6f3c10bd851a14
Code:service.FAILURE
at com.zimbra.common.service.ServiceException.FAILURE(ServiceException.java:258)
though I think this is only a symptom of this over in /var/log/zimbra.log:

Code:
Feb  3 12:29:27 mail zmconfigd[1232]: Fetching All configs
Feb  3 12:29:28 mail zmconfigd[1232]: All configs fetched in 0.16 seconds
Feb  3 12:29:28 mail zmmailboxdmgr[8107]: fopen(/opt/zimbra/log/zmmailboxd_manager.pid) failed: No such file or directory
Feb  3 12:29:28 mail zmmailboxdmgr[8107]: assuming no other instance is running
Feb  3 12:29:28 mail zmmailboxdmgr[8107]: file /opt/zimbra/log/zmmailboxd.pid does not exist
Feb  3 12:29:28 mail zmmailboxdmgr[8107]: assuming no other instance is running
Feb  3 12:29:28 mail zmmailboxdmgr[8107]: no manager process is running
Feb  3 12:29:28 mail zmconfigd[1232]: Executed: /opt/zimbra/bin/zmstorectl status norewrite returned 1 (30 - 13) (0.15 sec)
Feb  3 12:29:28 mail zmconfigd[1232]: Tracking service mailbox
Feb  3 12:29:29 mail zmmailboxdmgr[8114]: fopen(/opt/zimbra/log/zmmailboxd_manager.pid) failed: No such file or directory
Feb  3 12:29:29 mail zmmailboxdmgr[8114]: assuming no other instance is running
Feb  3 12:29:29 mail zmmailboxdmgr[8114]: file /opt/zimbra/log/zmmailboxd.pid does not exist
Feb  3 12:29:29 mail zmmailboxdmgr[8114]: assuming no other instance is running
Feb  3 12:29:29 mail zmmailboxdmgr[8114]: no manager process is running
Feb  3 12:29:29 mail zmconfigd[1232]: Executed: /opt/zimbra/bin/zmmailboxdctl status norewrite returned 1 (25 - 13) (0.08 sec)
Feb  3 12:29:29 mail zmconfigd[1232]: Tracking service mailboxd
Feb  3 12:29:35 mail zmconfigd[1232]: Watchdog: service antivirus status is OK.
Feb  3 12:29:35 mail zmconfigd[1232]: All rewrite threads completed in 0.00 sec
Feb  3 12:29:35 mail zmconfigd[1232]: All restarts completed in 0.00 sec
Feb  3 12:30:01 mail postfix/master[3374]: warning: process /opt/zimbra/postfix/libexec/showq pid 8250 killed by signal 11
Feb  3 12:30:01 mail postfix/master[3374]: warning: /opt/zimbra/postfix/libexec/showq: bad command startup -- throttling
Feb  3 12:30:11 mail postfix/cleanup[3377]: warning: private/proxymap socket: service dict_proxy_open: Connection reset by peer
Feb  3 12:30:11 mail postfix/master[3374]: warning: process /opt/zimbra/postfix/libexec/proxymap pid 8251 killed by signal 11
Feb  3 12:30:11 mail postfix/master[3374]: warning: /opt/zimbra/postfix/libexec/proxymap: bad command startup -- throttling
In particular, the bad command startup of showq and proxymap are new as of last night.

I also watched a tail -f /opt/zimbra/log/zmmailboxd.out but it looked pretty normal, here is what it spouted out during mailbox startup:
Code:
2014-02-03 12:10:19.347:INFO:oejsh.ContextHandler:started o.e.j.w.WebAppContext{/zimbraAdmin,file:/opt/zimbra/jetty-distribution-7.6.2.z4/webapps/zimbraAdmin/},/opt/zimbra/jetty-distribution-7.6.2.z4/webapps/zimbraAdmin
2014-02-03 12:10:19.386:INFO:oejs.DoSFilter:Whitelisted IP addresses: [127.0.0.1]
Total time for which application threads were stopped: 0.0991950 seconds
2014-02-03 12:10:21.023:INFO:oejpw.PlusConfiguration:No Transaction manager found - if your webapp requires one, please configure one.
Total time for which application threads were stopped: 0.0003530 seconds
2014-02-03 12:10:21.551:INFO:oejsh.ContextHandler:started o.e.j.w.WebAppContext{/zimlet,[file:/opt/zimbra/jetty-distribution-7.6.2.z4/webapps/zimlet/, file:/opt/zimbra/zimlets-deployed/]},/opt/zimbra/jetty-distribution-7.6.2.z4/webapps/zimlet
2014-02-03 12:10:21.593:INFO:oejs.NCSARequestLog:Opened /opt/zimbra/log/access_log.2014-02-03
Total time for which application threads were stopped: 0.0001320 seconds
2014-02-03 12:10:21.694:INFO:oejs.AbstractConnector:Started SelectChannelConnector@0.0.0.0:80
2014-02-03 12:10:21.739:INFO:oejus.SslContextFactory:Enabled Protocols [SSLv2Hello, SSLv3, TLSv1, TLSv1.1, TLSv1.2] of [SSLv2Hello, SSLv3, TLSv1, TLSv1.1, TLSv1.2]
Total time for which application threads were stopped: 0.0001290 seconds
2014-02-03 12:10:21.742:INFO:oejs.AbstractConnector:Started SslSelectChannelConnector@0.0.0.0:443
2014-02-03 12:10:21.747:INFO:oejus.SslContextFactory:Enabled Protocols [SSLv2Hello, SSLv3, TLSv1, TLSv1.1, TLSv1.2] of [SSLv2Hello, SSLv3, TLSv1, TLSv1.1, TLSv1.2]
Total time for which application threads were stopped: 0.0026600 seconds
2014-02-03 12:10:21.760:INFO:oejs.AbstractConnector:Started SslSelectChannelConnector@0.0.0.0:7071
2014-02-03 12:10:21.805:INFO:oejs.AbstractConnector:Started SelectChannelConnector@0.0.0.0:7072
Total time for which application threads were stopped: 0.0015690 seconds
At this point, I'm kind of stuck, I'm not even sure what logs to check at this point to figure out why showq and proxymap are throwing warnings (assuming that's the issue). Any help would be very appreciated.

Finally, I'm running zimbra 8.0.0 on ubuntu 10.04, it's been working great for well over a year, so this is absolutely a new development.
Thank you for your time.