Yes it was. It took years before I had a limit. I used to use gmail like google drive well before drive existed. There was even a tool called gmaildrive(0).
I'm surprised too, but the screenshot showing "You are are currently using ... of your 1000GB" brings back memories. Maybe it's because back then 1GB of email storage seemed essentially unlimited?
I remember those, you got 5 of them... later Google Wave also had invites .. which was cool but ended up in the graveyard anyway... Lifehacker's Gina Trapani even wrote a guide to Google Wave but I believe Wave was killed right before after it was published
Google later changed it to “unlimited” which increased daily by an MB or so. At some point settled at 15 GB.