Email Not Found and Loading All Emails in a Folder?

[Danno321]

I use Thunderbird and Zimbra desktop, ZD mostly. I know of an email in my sent folder that is over 1.5 years old. If I search for it in ZD, ZD does not find it. TB finds. Also, ZD will not load ALL the emails on my SENT folder so I can quickly scroll the list; is there a key command on Mac OS X to force a complete folder load? TIA