Not tested (yet)!
1. stop zimbra
1a. check if every process is really stopped. don’t want to see stalled mysql or something – happened to me once
2. tar zimbra installation folder
3. tar /var/lib/rpm !!! (I forget often to do this)
4. START ZIMBRA!!! (else upgrade could fail)
5. upgrade
6. if everything works, delete backups, else untar and try again
zmprov mcf -zimbraGalLdapAttrMap zimbraMailDeliveryAddress,zimbraMailAlias,mail=email,email2,email3,email4,email5,email6,email7,email8,email9,email10,email11,email12,email13,email14,email15,email16
zmprov mcf +zimbraGalLdapAttrMap zimbraMailCanonicalAddress,mail=email
zmprov fc config