Facebook is having another one of its all-hands-on-deck press events next Monday and the speculation this time around, a la the telegram-esque design of the invite, is that the company will unveil its “Gmail killer“.

The offering, dubbed “Project Titan”, would potentially offer @facebook.com email addresses with POP access, not to mention integration with Microsoft’s Office Web Apps.

The rumor has been floating around for a while now, but TechCrunch’s Jason Kincaid writes this morning that sources confirmed that “a web-based email client […] is indeed what’s coming on Monday during Facebook’s special event, alongside personal @facebook.com email addresses for users.”

Kincaid isn’t the only one saying Facebook is getting into the email game. ZDNet’s Microsoft reporter Mary-Jo Foley says she’s ditching her deeply-ingrained conviction to only report tips that come from three independent sources and confirming this as a “(Not so) Crazy Microsoft Rumor“.

Foley says she has a source close to Microsoft who confirms that Facebook will be unveiling a full-fledged email offering, not “a mere revamp”, that will include Office Web Apps integration. This is certainly not far fetched, as Facebook and Microsoft are already cozy with their Bing integration and the Instant Personalization partnership around Microsoft’s Docs.com.

If true, the announcement would certainly answer the “why now” that’s lingered around Google and Facebook’s ongoing battle over your data this past week – and from what it looks like, it’s true. So much for email topping Facebook for keeping in touch, huh?