We're aware of a problem with Gmail affecting a small subset of users. The affected users are unable to access Gmail. We will provide an update by February 24, 2009 6:30 AM PST detailing when we expect to resolve the problem. Please note that this resolution time is an estimate and may change.
From: http://groups.google.com/group/Gmail-Help-Announcements-and-...
We tried Mosso out for a while about a year and a half ago, we were not impressed - frequents outages and performance issues. Also, MySQL DB connectivity often dropped. They responded relatively quickly but outages were too frequent to justify staying with them.