Under my Zimbra 5.0.4 under RHEL 5 64 bit, com_zimbra_phone zimlet does not work. No telephone numbers are highlighted, both in contacts and email views. Tried with many differently formatted numbers (with/without +1, with/without +39, 0039, etcetera).
No errors when undeployed/redeployed, at least by looking at mailbox.log. Other zimlets (date, email, url, ymaps) work flawlessly.

I'd post more information, only if had something more to report! Let me know if you guys come up with any suggestion/info request.

Thanks in advance!