 Move from 5.0.16 Fodora 32 bits. ==> 5.016 Ubuntu 64 bits.
Move from Zimbra 5.0.16 32 bits. Fedora core7 to Zimbra 5.0.16 64 bits. Ubuntu 8.04 successfully by document from Network Edition: Moving from 32-bit to 64-bit Server - Zimbra :: Wiki
After move upgrade from 5.0.16 64 bits. ==> 5.0.18 64 bits. is very Smooth.
Thank very much Zimbra Team  .
Kernel
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Zimbra 5.0.19 on Dell R710| Ubuntu 8.04 x86_64, 8 GB. RAM, Dual Quad Xeon, 4X146 GB. SAS.
Zimbra install as Multi Server MTA. & LDAP.+Mailbox server |