gmail.com 50% spammers ?!

with a mysql select on my forum db for @gmail users, it seems, that 50% are spammers, and only the other 50% are regular accounts.

Spam came back!

New kind of spam is hiting my forum.

The mail server is everytime the same "gmail.com". Language and time are correct for my italian forum. No other informations are provided in the user account. No websites, no signatures. I can't block this recognizing user infos.

I must have an idea!