Emails remain in Active queue

[evollution]

Dear sirs

We are using the 5.0.16_GA_2921.RHEL5.FOSS Apr 29, 2009 Zimbra version .. actually we have several problems that I couldn't resolve through forums or wiki help pages ..

We run this installation in a Dell PowerEdge 2950 III server
4 GB RAM Memory
265 GB HD
2xIntel Xeon@1.60 GHz

We are using Zimbra from one year ago without problems ..

By june 6th, I upgraded from 5.0.10 version to 5.0.16 ... no problem was detected ..

By june 17th, one of our clients had problems with their mail server. We receive the emails to this client and then relay to their server, but their server was unreacheable and email keep in deferred queue.

By june 18th, Antispam start to fail.. we have more than 20,000 deferred messages for the client server with problems. We had to disable antivirus/antispam check to solve this issue.

By june 20th, I installed new memory modules to the server. The server had 4 GB of RAM and I added 4 GB to get 8 GB installed. Zimbra doesn't start. I tried to reinstall several times but was unsuccesful.

I create a backup, uninstall zimbra and reinstall again. The new clean installation works well, but I was not able to import data from the old installation. Enven we lost database connection because change of passwords.

Yesterday by night, I removed the memory modules and start the server with the old kernel that was working. I use a june 6th backup. It was working well but now I have the same antispam problem and emails remain in Active queue and SMTP sessions are very slow (almost 10 second for a telnet at port 25 reply).

The nginx reports that is not running ..

Any idea about this ??