Though Google’s exclusive new e-mail service has not made its public debut, Gmail, only available through a referral from friends, already has a core of users in Cambridge.

Citing the privacy of its customers, Google’s public relations department would not comment on inquiries about Gmail enrollment figures. But the service has already taken a secure hold at Harvard.

After news of the search-engine’s newest venture spread last summer, dozens of students have switched to Gmail as their primary e-mail client, citing its extensive search features, speed and unique “conversation” feature that organizes e-mail messages according to their authors and replies.

“Gmail is fast, and lets you save your password, unlike Yahoo! mail,” said Timothy H. Wong ’05. “Also, you can reply to a new message without loading a new window. This was a small revolution which astounded me.”

Gmail users said that the new system has a larger storage capacity than webmail and is more user-friendly than the text-based Pine e-mail client. It also avoids the security holes of PC e-mail clients like Microsoft Outlook.

Gmail’s 1000 megabytes (MB) of storage—compared to FAS webmail’s 100 MB of storage—also means that a Gmail user will never have to delete potentially important old mail.

Perhaps the greatest allure of Gmail lies not in its mammoth capacity or its convenient search features, but in its exclusivity. Because it is still in the beta testing stage while Google perfects its antivirus software, a Gmail account is only available to those who have friends willing to pass on a limited number of invitations.

As a result, Gmail “invites” have become a precious commodity at Harvard and beyond. Websites organizing the trading of Gmail invites have sprung up in droves, although Wong pointed out that the increasing number of accounts also makes having an account increasingly less exceptional.

“Ask anyone and they’ll have a free invite for you...If anyone doesn’t already have Gmail, they don’t deserve to have it ever,” he said.

In response to the impending juggernaut of Gmail, other free e-mail clients have upped the ante and increased their own storage space—although none can still compare to Gmail’s capacity.

Over the summer, Yahoo! Mail expanded its free account storage space to 100 MB from 10 MB in an effort to retain users. Hotmail embarked on a similar move and now has a 250 MB capacity.

Student groups are also taking advantage of the new service.

“I have two Gmail accounts, one specifically for all correspondence for a conference I’m organizing and one general one that I intend to use after my FAS account is no longer active,” said Anna Franekova ’05.