Gmail, the email service that I resisted for years before finally embracing, may become just-about irresistible. Andrew Fogg of “Enterprise 2.0″ consulting firm Kusiri says he saw a preview of offline versions of Gmail and Google Calendar at the Google offices. Using Google’s Gears technology, they should be available in six weeks, he says. This is a really important feature for Gmail, because right now all of a Gmail user’s messages remain online (although you could pull them onto your desktop with other services like Microsoft’s Outlook and Mozilla’s Thunderbird). That’s really annoying if you want to go through emails but don’t have internet access — VentureBeat Editor Matt Marshall, for example, does some of his best work while on the train. It’s also a huge problem if the Gmail servers go down. Those drawbacks are why I left my Gmail account dormant for a while, although features like Google search, tags and conversation-threading lured me in a couple of years ago. Offline access would really eliminate the last major barrier to using Gmail, although that doesn’t necessarily mean the situation is dire for competitors. Outlook has plenty of useful features of its own, and it supports cool add-ons produced by startups like Xobni. Fogg says users will also be able to synchronize their Google contacts using SyncML technology, which could be related to improving sync capabilities with Apple’s iPhone. The Web site Google Operating System spotted Fogg’s comments, which were posted on Twitter, and Webware posted this response from Google: “We’re working on Gears-enabling a number of our products, but we don’t have a specific timeline to announce.” [Update: I just received an email from Google with the same statement.] All the offline capability that Gears is enabling should make it easier for Google to pitch its products for use in a corporate environment. I’m really in love with Gears (which launched in May 2007) myself — the number one reason I switched browsers from Camino to Firefox was to use Gears to edit my Google Docs offline, and this just makes me happier that I made the switch. WordPress is using Gears for offline blogging, too.