Palm Treo 650
To setup syncing on the Palm Treo 650, setup your account in Versamail as an "ActiveSync" account. Use your regular username and password. Versamail can be configured to automatically sync the Zimbra ActiveSync account on a schedule as defined by the user.
By default the Treo 650 only supports syncing of E-mail and Calendar over-the-air. In order for contacts, task & notes to be sync'd over-the-air you will need to patch activesync  and update VersaMail to 3.5  which together costs about $14.00 USD
Note that VersaMail v3.5 has problems with self-signed certificates. If a self-signed certificate is being used then the root for that certificate needs to be imported using the Palm Certificate Modification Tool 
If a "QuickInstall.exe not found" error occurs even after following the instructions for resolution at the download page, try looking in the folder where the certificate file that was added to PalmCertificates.exe is located. The certs.pdb file was likely generated anyway and can be installed manually.
If HotSync fails to install the certs.pdb saying that the file already exists you may need to do a soft reset of the device first as the file may be locked by an application.
If even the soft reset does not allow the new certs.pdb to be installed the old file may need to be removed manually using something like FileZ.  When browsing the Palm file system with this utility it will be helpful to uncheck the ROM option and be aware that the certs.pdb file will be listed as "CertMgrDB".
If the manual deletion is not possible due to file locking the file can actually still be renamed. A rename, followed by another soft reset, will (finally!) allow the new certs.pdb to be installed. At this point there will be both the new CertMgrDB file and whatever the old one was renamed to. It is not necessary to actually delete the old renamed file, another soft reset will cause it to silently disappear with no ill effects and the new one will automatically be picked up in its place.