I started using Netscape Communicator -- Navigator, Mail, and Composer -- from the very beginnings in 1994 when it was Mosaic. I migrated from CompuServe and Spyglass as soon as I could; I'd been on CompuServer since the 1980's.
I've always preferred the Netscape application designs, and thankfully Firefox and Thunderbird (and Seamonkey) have largely maintained them.
Netscape Communicator. Wow, a blast from the past, and yes, I always loved using that as well. I can’t stand Firefox though I do use Thunderbird.