Certificate issues - multiple certificates

[jwf6911]

Hello there,

I'm running Zimbra OE 5.0.5GA. When I click "View Certificate" from the admin console, I got three different certificates with DIFFERENT expiration dates. See below -

Server Name: mydomain.com

1) Certificate for Zimbra ldap Service:

Subject: /C=US/ST=N/A/O=Zimbra Collaboration Suite/CN=mydomain.com
Issuer: /C=US/ST=N/A/L=N/A/O=Zimbra Collaboration Suite
Validation Days: May 7 20:21:34 2007 GMT - May 6 20:21:34 2008 GMT
Subject Alternative Name:

2) Certificate for Zimbra mailboxd Service:

Subject: /C=US/ST=NA/L=NA/O=Zimbra/OU=Zimbra/CN=mydomain.com
Issuer: /C=US/ST=NA/L=NA/O=Zimbra/OU=Zimbra/CN=mydomain.com
Validation Days: May 7 20:21:34 2007 GMT - May 6 20:21:34 2009 GMT
Subject Alternative Name:

3) Certificate for Zimbra mta Service:
Subject: /C=US/ST=N/A/O=Zimbra Collaboration Suite/CN=mydomain.com
Issuer: /C=US/ST=N/A/L=N/A/O=Zimbra Collaboration Suite
Validation Days: May 3 15:47:09 2007 GMT - May 2 15:47:09 2008 GMT
Subject Alternative Name:

My questions are
1) why there are three different certificates? Can we use ONE for all?
2) When I use web mail interface, the security certificate information indicates the expiration date is May 6, 2009, but the security certificate error message in my Thunderbird shows the expiration date is May 2, 2008. How can I fix this certificate inconsistency problem?

Thanks!