I've been getting delays in the WebUI when sending emails, and on occasion getting the following error:

"The Server appears to be slow to respond, and may be unavailable Press the button to cancel your request"
It has been working for the longest time without problems until this the last month.

Steps I have taken so far to try to resolve:
1. Performance Tuning: Performance Tuning Guidelines for Large Deployments - Zimbra :: Wiki
2. Migrated to a faster server with more memory (24GB).
3. Upgraded to the Zimbra 7.2.1 (delayed upgrading to 8.0 until I figure out this current problem.)

CPU Load has gone down considerably after upgrades, but the time delay when sending emails still persists. Any insight would be greatly appreciated. Thank you.

The following is the output from logs as soon as I send the message:

These are in the /var/log/mail.log
Nov 19 10:07:16 mail postfix/smtpd[2402]: connect from mail.cityofalachua.org[172.16.0.7]
Nov 19 10:07:16 mail postfix/smtpd[2402]: 5BC39700A95: client=mail.cityofalachua.org[172.16.0.7]
Nov 19 10:07:16 mail postfix/cleanup[2403]: 5BC39700A95: message-id=<1237465034.1328.1353337636326.JavaMail.root@cityof alachua.org>
Nov 19 10:07:17 mail slapd[1375]: slap_queue_csn: queing 0x7fa0de803420 20121119150717.609316Z#000000#000#000000
Nov 19 10:07:17 mail slapd[1375]: slap_graduate_commit_csn: removing 0xac22cc0 20121119150717.609316Z#000000#000#000000
Nov 19 10:07:27 mail postfix/qmgr[2745]: 5BC39700A95: from=, size=1627, nrcpt=1 (queue active)

Nov 19 10:07:27 mail postfix/smtpd[2402]: disconnect from mail.cityofalachua.org[172.16.0.7]
Nov 19 10:07:27 mail postfix/smtp[2411]: 5BC39700A95: to=, relay=mailscanner.cityofalachua.org[172.16.0.8]:25, delay=11, delays=11/0.01/0/0.02, dsn=2.0.0, status=sent (250 2.0.0 Ok: queued as 443067C089)
Nov 19 10:07:27 mail postfix/qmgr[2745]: 5BC39700A95: removed
These are in the /opt/zimbra/log/mail.log
2012-11-19 10:07:07,116 INFO [Pop3Server-10] [] ProtocolHandler - Handler exiting normally
2012-11-19 10:07:16,323 INFO [btpool0-60://mail.cityofalachua.org/service/soap/SendMsgRequest] [name=ga_saintvil@cityofalachua.org;mid=264;ip=10.1 0.10.47;ua=ZimbraWebClient - FF3.0 (Win)/7.2.1_GA_2790;] soap - SendMsgRequest
2012-11-19 10:07:16,344 INFO [btpool0-60://mail.cityofalachua.org/service/soap/SendMsgRequest] [name=ga_saintvil@cityofalachua.org;mid=264;ip=10.1 0.10.47;ua=ZimbraWebClient - FF3.0 (Win)/7.2.1_GA_2790;] mailop - Adding Message: id=38655, Message-ID=<1237465034.1328.1353337636326.JavaMail.root@cityof alachua.org>, parentId=-1, folderId=5, folderName=Sent.
2012-11-19 10:07:16,350 INFO [btpool0-60://mail.cityofalachua.org/service/soap/SendMsgRequest] [name=ga_saintvil@cityofalachua.org;mid=264;ip=10.1 0.10.47;ua=ZimbraWebClient - FF3.0 (Win)/7.2.1_GA_2790;] smtp - Sending message to MTA at mail.cityofalachua.org: Message-ID=<1237465034.1328.1353337636326.JavaMail.root@cityof alachua.org>, replyType=r
2012-11-19 10:07:16,361 INFO [ImapServer-4] [name=ga_saintvil@cityofalachua.org;mid=264;ip=172. 16.0.101;ua=com.motorola.motoemail;] imap - selected folder INBOX/Current Projects/Security Cameras
2012-11-19 10:07:16,897 INFO [btpool0-62://mail.cityofalachua.org/service/soap/NoOpRequest] [name=ga_saintvil@cityofalachua.org;mid=264;ip=10.1 0.10.47;ua=ZimbraWebClient - FF3.0 (Win)/7.2.1_GA_2790;] soap - NoOpRequest
2012-11-19 10:07:17,221 INFO [ImapServer-4] [name=ga_saintvil@cityofalachua.org;mid=264;ip=172. 16.0.101;ua=com.motorola.motoemail;] imap - selected folder INBOX/Correspondence/Gainesville Police Department
2012-11-19 10:07:17,403 INFO [btpool0-62://mail.cityofalachua.org/service/soap/NoOpRequest] [name=ga_saintvil@cityofalachua.org;mid=264;ip=10.1 0.10.47;ua=ZimbraWebClient - FF3.0 (Win)/7.2.1_GA_2790;] soap - NoOpRequest
2012-11-19 10:07:17,548 INFO [ScheduledTask-7] [name=apd.primary@apd.cityofalachua.org;mid=318;ds= apd.local;] datasource - Requested import.
2012-11-19 10:07:17,548 INFO [ScheduledTask-7] [name=apd.primary@apd.cityofalachua.org;mid=318;ds= apd.local;] datasource - Importing data for data source 'apd.local'
2012-11-19 10:07:17,615 INFO [ScheduledTask-7] [name=apd.primary@apd.cityofalachua.org;mid=318;ds= apd.local;] datasource - Import completed for data source 'apd.local'
2012-11-19 10:07:17,744 INFO [ImapServer-4] [name=ga_saintvil@cityofalachua.org;mid=264;ip=172. 16.0.101;ua=com.motorola.motoemail;] imap - selected folder INBOX/Support Tickets
2012-11-19 10:07:17,910 INFO [btpool0-62://mail.cityofalachua.org/service/soap/NoOpRequest] [name=ga_saintvil@cityofalachua.org;mid=264;ip=10.1 0.10.47;ua=ZimbraWebClient - FF3.0 (Win)/7.2.1_GA_2790;] soap - NoOpRequest
2012-11-19 10:07:18,417 INFO [btpool0-62://mail.cityofalachua.org/service/soap/NoOpRequest] [name=ga_saintvil@cityofalachua.org;mid=264;ip=10.1 0.10.47;ua=ZimbraWebClient - FF3.0 (Win)/7.2.1_GA_2790;] soap - NoOpRequest
2012-11-19 10:07:18,659 INFO [ImapServer-4] [name=ga_saintvil@cityofalachua.org;mid=264;ip=172. 16.0.101;ua=com.motorola.motoemail;] imap - selected folder INBOX/Current Projects/Visit Alachua
2012-11-19 10:07:19,166 INFO [btpool0-62://mail.cityofalachua.org/service/soap/NoOpRequest] [name=ga_saintvil@cityofalachua.org;mid=264;ip=10.1 0.10.47;ua=ZimbraWebClient - FF3.0 (Win)/7.2.1_GA_2790;] soap - NoOpRequest
2012-11-19 10:07:19,447 INFO [ImapServer-4] [name=ga_saintvil@cityofalachua.org;mid=264;ip=172. 16.0.101;ua=com.motorola.motoemail;] imap - selected folder INBOX/APD/LInX
2012-11-19 10:07:19,953 INFO [btpool0-62://mail.cityofalachua.org/service/soap/NoOpRequest] [name=ga_saintvil@cityofalachua.org;mid=264;ip=10.1 0.10.47;ua=ZimbraWebClient - FF3.0 (Win)/7.2.1_GA_2790;] soap - NoOpRequest
2012-11-19 10:07:19,964 INFO [ImapServer-4] [name=ga_saintvil@cityofalachua.org;mid=264;ip=172. 16.0.101;ua=com.motorola.motoemail;] imap - selected folder INBOX/COA/DynDNS
2012-11-19 10:07:20,453 INFO [ImapServer-4] [name=ga_saintvil@cityofalachua.org;mid=264;ip=172. 16.0.101;ua=com.motorola.motoemail;] imap - selected folder INBOX/Online Order Receipts/DynDNS
2012-11-19 10:07:20,470 INFO [btpool0-62://mail.cityofalachua.org/service/soap/NoOpRequest] [name=ga_saintvil@cityofalachua.org;mid=264;ip=10.1 0.10.47;ua=ZimbraWebClient - FF3.0 (Win)/7.2.1_GA_2790;] soap - NoOpRequest
2012-11-19 10:07:20,978 INFO [btpool0-62://mail.cityofalachua.org/service/soap/NoOpRequest] [name=ga_saintvil@cityofalachua.org;mid=264;ip=10.1 0.10.47;ua=ZimbraWebClient - FF3.0 (Win)/7.2.1_GA_2790;] soap - NoOpRequest
2012-11-19 10:07:21,373 INFO [ImapServer-4] [name=ga_saintvil@cityofalachua.org;mid=264;ip=172. 16.0.101;ua=com.motorola.motoemail;] imap - selected folder INBOX/COA/EMC
2012-11-19 10:07:21,881 INFO [btpool0-62://mail.cityofalachua.org/service/soap/NoOpRequest] [name=ga_saintvil@cityofalachua.org;mid=264;ip=10.1 0.10.47;ua=ZimbraWebClient - FF3.0 (Win)/7.2.1_GA_2790;] soap - NoOpRequest
2012-11-19 10:07:21,919 INFO [ImapServer-4] [name=ga_saintvil@cityofalachua.org;mid=264;ip=172. 16.0.101;ua=com.motorola.motoemail;] imap - selected folder INBOX/Online Order Receipts/GoDaddy
2012-11-19 10:07:22,426 INFO [btpool0-62://mail.cityofalachua.org/service/soap/NoOpRequest] [name=ga_saintvil@cityofalachua.org;mid=264;ip=10.1 0.10.47;ua=ZimbraWebClient - FF3.0 (Win)/7.2.1_GA_2790;] soap - NoOpRequest
2012-11-19 10:07:22,492 INFO [ImapServer-4] [name=ga_saintvil@cityofalachua.org;mid=264;ip=172. 16.0.101;ua=com.motorola.motoemail;] imap - selected folder INBOX/COA/AXIS Communications
2012-11-19 10:07:22,962 INFO [ImapServer-4] [name=ga_saintvil@cityofalachua.org;mid=264;ip=172. 16.0.101;ua=com.motorola.motoemail;] imap - selected folder INBOX/COA/Security Cameras
2012-11-19 10:07:22,999 INFO [btpool0-62://mail.cityofalachua.org/service/soap/NoOpRequest] [name=ga_saintvil@cityofalachua.org;mid=264;ip=10.1 0.10.47;ua=ZimbraWebClient - FF3.0 (Win)/7.2.1_GA_2790;] soap - NoOpRequest
2012-11-19 10:07:23,505 INFO [btpool0-62://mail.cityofalachua.org/service/soap/NoOpRequest] [name=ga_saintvil@cityofalachua.org;mid=264;ip=10.1 0.10.47;ua=ZimbraWebClient - FF3.0 (Win)/7.2.1_GA_2790;] soap - NoOpRequest
2012-11-19 10:07:23,794 INFO [ImapServer-4] [name=ga_saintvil@cityofalachua.org;mid=264;ip=172. 16.0.101;ua=com.motorola.motoemail;] imap - selected folder INBOX/Online Order Receipts/Dell
2012-11-19 10:07:24,266 INFO [ImapServer-4] [name=ga_saintvil@cityofalachua.org;mid=264;ip=172. 16.0.101;ua=com.motorola.motoemail;] imap - selected folder INBOX/COA/GoDaddy
2012-11-19 10:07:24,302 INFO [btpool0-62://mail.cityofalachua.org/service/soap/NoOpRequest] [name=ga_saintvil@cityofalachua.org;mid=264;ip=10.1 0.10.47;ua=ZimbraWebClient - FF3.0 (Win)/7.2.1_GA_2790;] soap - NoOpRequest
2012-11-19 10:07:24,764 INFO [ImapServer-4] [name=ga_saintvil@cityofalachua.org;mid=264;ip=172. 16.0.101;ua=com.motorola.motoemail;] imap - selected folder INBOX/COA/Adobe VLM
2012-11-19 10:07:24,808 INFO [btpool0-62://mail.cityofalachua.org/service/soap/NoOpRequest] [name=ga_saintvil@cityofalachua.org;mid=264;ip=10.1 0.10.47;ua=ZimbraWebClient - FF3.0 (Win)/7.2.1_GA_2790;] soap - NoOpRequest
2012-11-19 10:07:25,313 INFO [btpool0-62://mail.cityofalachua.org/service/soap/NoOpRequest] [name=ga_saintvil@cityofalachua.org;mid=264;ip=10.1 0.10.47;ua=ZimbraWebClient - FF3.0 (Win)/7.2.1_GA_2790;] soap - NoOpRequest