5점중 1점 받음

You might say who cares, but not me. I have an addressbook with people who don't have some emails and when trying to "sync" / upload them to google via this Zindus plugin, google pukes and says that the entries are empty. So I guess it's not really Zindus' fault, but it sure ain't a solution for me.

이 검토는 현재 부가 기능의 이전 (0.7.8) 버전에 대한 것입니다. 

Hi Danshu, Thunderbird and Google contact fields don't match exactly. So like you say, you can have a perfectly reasonable Thunderbird contact that maps to a completely empty Google contact. And vice versa. Those contacts can't be synced.

The easiest workaround is to give them an email address - even a fake one is ok.